WO2004074709A1

WO2004074709A1 - Impact absorbing structures

Info

Publication number: WO2004074709A1
Application number: PCT/GB2004/000244
Authority: WO
Inventors: Tommy Scott; Jonathan Patty
Original assignee: Survitec Group Limited
Priority date: 2003-02-20
Filing date: 2004-01-22
Publication date: 2004-09-02
Also published as: GB0303911D0; GB2398594A

Abstract

An impact absorbing structure comprises a main chamber (10) supported by an inflatable second chamber formed by struts (21, 22) and walls (11, 12, 15, 16) so that the main chamber (10) deforms when impacted by a moving body to provide controlled deceleration of the body. The structure can be used to form a crash barrier.

Description

IMPACT ABSORBING STRUCTURES

The invention relates to impact absorbing structures.

Impact absorbing structures are used for safety to decelerate a body or bodies in a

controlled manner. They can be used in sports such as motor sports, and winter sports

where persons or objects moving at speed are likely to be injured or damaged due to

uncontrolled decelerations. They can also be used in civil applications, in, for

example, impact absorbing structures placed on public highways or military

applications for protecting persons or inanimate objects dropped from a height.

Examples of such barriers currently in use include netting, walls of motor tyres and

metal barriers.

According to a first aspect of the invention, there is provided an impact absorbing

structure comprising at least one inflatable member conforming a flexible cover to

produce a chamber, the chamber deforming when impacted by a moving body to

provide controlled deceleration of the body.

According to a second aspect of the invention, there is provided a crash barrier

comprising a plurality of impact absorbing structures according to the first aspect of

the invention in which each chamber has an associated front wall forming an impact

surface, structures being placed side by side so that the front walls form a continuous

impact surface. The following is a more detailed description of an embodiment of the invention, by

way of example, reference being made to the accompanying drawings in which:-

Figure 1 is a schematic perspective view of an impact absorbing structure,

Figure 2 is a schematic plan view from above of part of a crash barrier formed by a

number of impact absorbing structures of the kind shown in Figure 1 placed side by

side and with a protective cover,

Figure 3 is a schematic cross section through a part of a drop thread fabric for use

in the impact absorbing structure of Figure 1, and

Figure 4 is a detail on X of Figure 3.

Referring first to Figure 1, the impact absorbing structure comprises a closed outer

chamber indicated generally at 10 formed by a cover having a front wall 11, a rear

wall 12, an upper surface 13, a lower surface 14 and first and second side walls 15, 16.

As seen in Figure 1, the front wall 11 and the rear wall 12 are significantly longer

than the first and second side walls 15, 16. For example, the front wall 11 and the rear

wall 12 maybe 8 metres in length and the first and second side walls 15,16 1.15 metres

in length with a height of 1 metre. The chamber 10 has, in plan view from above, the

form of a parallelepiped in which the first side wall 15 makes an acute angle with the

front wall 11 and the second side wall 16 makes a complimentary obtuse angle with

the front wall 11. The front wall 11, the rear wall 12 and the first and second side walls 15,16 are

formed from a drop stitch fabric of the kind shown in Figures 3 and 4. Referring to

those figures, the fabric comprises a first textile layer 17 interconnected to a second

textile layer 18 by a plurality of threads shown schematically at 26. The textile layers

may be a woven polyester, polyamide or similar material. The threads maybe made

from polyester, polyamide or similar material. Both the first layer 17 and the second

layer 18 are provided with an inner coating which may be of any suitable cross-linked

polymeric material such as polychloroprene or a non cross-linked thermoplastic

material, a textile chaffing layer 19 and an outer coating 20 which may be of any

suitable cross-linked polymeric material or such as polychloroprene or a non cross-

linked thermoplastic material. An elongate rectangular sheet of such thread material

has the side edges of the first textile layer 17 connected to the side edges of the second

textile layer 19 to form a rectangular closed panel. The panel is provided with an air

inlet (not shown) to allow it to be inflated. Appropriately sized panels are used to

form the front and rear walls 11, 12 and the first and second side walls 15, 16 with all

the walls 11, 12, 15, 16 communicating with one another to form a unitary inner

chamber.

The upper surface 13 and the lower surface 14 are formed from appropriately sized

sheets of flexible air impervious material such as a plastic covered fabric material.

The outer chamber is conformed by a plurality of inflatable struts 21. Each strut 21 is formed by an inflatable tube of an air impermeable material. As seen in Figure 1, the

struts 21 extend between an inner surface of the front wall 11 and an inner surface of

the rear wall 12, between an inner surface of the front wall 11 and an inner surface of

the first side wall 15 and between an inner surface of the rear wall 12 and an inner

surface of the second side wall 16. At the connection between each strut 21 and wall

11, 12, 15, 16, the strut 21 is in communication with the associated wall to form part

of the unitary inner chamber with the walls 11, 12, 15, 16. It will also be seen that

none of the struts 21 lies in a horizontal plane; the struts 21 are angled to the

horizontal and are angled relative to vertical planes normal to the front wall 11. The

reason for this will be explained below. There are also triangulation struts 22 which

are formed identically to the struts 21 but which extend between adjacent pairs of

struts 21 to provide an element of rigidity to prevent the front wall 11 and the rear wall

12 becoming mis-aligned. The triangulation struts 22 are also in communication with

the associated walls 11, 12, 15, 16 to form part of the unitary inner chamber.

Referring next to Figure 2, in use, a plurality of structures of the kind shown in Figure

1 are placed side by side to form a continuous crash barrier. As seen in Figure 2, in

this disposition, each first side wall 15 abuts against the second side wall 16 of the

next adjacent structure to provide overlap between the structures in a direction normal

to the front walls 11 of the structures. The front walls 11 are covered by a continuous

protective sheet or cover indicated generally at 23 formed by an end to end succession of panels 24. Each panel is formed from a drop thread fabric of the kind shown in

Figures 3 and 4 with closed edges so that the panel is inflatable to form a third

chamber independent of the outer and inner chambers. The protective sheet 23 may

be covered by an additional layer or layers of material to provide fire retardency and to

provide resistance to puncturing. In addition, such a layer may also provide a means

of anchoring the front edge of the barrier to the ground and can provide advertising

space.

The barrier described above with reference to the drawings is designed to be used to

absorb the impact of vehicles and more particularly motorcycles. The individual

structures can be readily transported in a deflated condition and taken to a required

location. There, unitary inner chamber formed by the struts 21 , the triangulation struts

22, the front wall 11, the rear wall 12 and the first and second side walls 15, 16 is

inflated. The pressure in this inner chamber may, for example, be 5.17kPa (0.75psi).

This conforms the outer chamber to the shape shown in Figures 1 and 2. In addition,

air under pressure is introduced into the outer chamber 10. The pressure in the outer

chamber 10 is lower than the pressure in inner chamber and may be as low as 0.17kPa

(0.025psi). The structures are placed side by side as shown in Figure 2 and the sheet

23 formed by the panels 24 are inflated and located on the front walls 11.

In the barrier, the inflated walls 11, 12, 15, 16 and the inflated struts 21, 22, the parts

making up the inner chamber, are designed simply to provide sufficient rigidity to allow the structure to maintain and retain its shape. The effect of any impact is

absorbed principally by the outer chamber 10. When a body such as a motorcycle,

impacts the front wall 11 , the chamber 10 deforms to absorb the load. The pressure in

the struts 21 and the triangulation struts 22 and their diameter are such, that under

such impact loads, they simply buckle. This is assisted by the fact that none of the

struts 21,22 extends normal to the front wall 11. The same is true of the front wall

11; under impact load it simply bends inwardly.

After impact the buckled struts 21 and triangulation struts 22 and any buckled walls

11, 12, 15 and 16 straighten to re-conform the outer chamber but do not product large

forces while straightening. This prevents the structure from returning rapidly to its

original shape and keeps rebound velocity to a minimum.

The third chamber formed by the sheet 23 has as its principle purpose to reduce if not

eliminate the chance of an impacting body from entering the gap between two

adjacent structures. Its presence is not essential for the proper functioning of the

structure and if, for example, a sharp edge or an impacting body were to burst the

panels 24 making up the sheet 23, the structure would still function effectively.

It will be appreciated that the structure and the barrier described above with reference

to the drawings are designed specifically to take the impact of a motorcycle. Parts

may be differently dimensioned and arranged to take other impacts such as the impact of a car or a person performing a sport such as skiing. In addition, the structure could

be designed to absorb vertically downward impact loads. It will also be appreciated

that there are many other variations that can be made to the structure described above

with reference to the drawings. For example, while the front wall 11, rear wall 12 and

first and second side walls 15, 16 of the cover have been described as being inflatable;

they need not be inflatable. They could be formed by non-inflatable panels of suitable

material. In addition, while the chamber 10 is described above as closed; it need not

be closed. There could be provided vents which could provide controlled venting and

air from the interior of the chamber 10 in the event of an impact and control the return

of air after impact. Where the walls 11, 12, 15 and 16 are not inflated, the shape of

the chamber 10 may be defined by additional inflatable tubes. For example, there

could be a framework of tubes in the shape of a parallelepiped supporting the walls

11, 12, 15 and 16. Although the front wall 11 is shown as vertical; it need not be

vertical. It could subtend an angle to the vertical from example 5° or 10° either

forwards or backwards.

Claims

1. An impact absorbing structure comprising at least one inflatable member (21)

conforming a flexible cover (11, 12, 13, 14, 15, 16) to produce a chamber (10), the

chamber (10) deforming when impacted by a moving body to provide controlled

deceleration of the body.

2. A structure according to claim 1 wherein the cover includes a front wall (11)

supported by the at least one inflatable member (21) and forming an impact surface.

3. A structure according to claim 2 wherein the front wall (11) is vertical.

4. A structure according to claim 4 wherein the front wall (11) has a front surface and

a rear surface and wherein the at least one inflatable member comprises a plurality of

inflatable struts (21) extending away from the rear surface of the front wall (11) to

support the front wall (11).

5. A structure according to claim 4 wherein at least some of said inflatable struts (21)

are connected between the front wall (11) and a rear wall (12) of the chamber (10).

6. A structure according to claim 4 or claim 5 wherein the struts (21) extend away

from the front wall (11) at an angle to a horizontal plane.

7. A structure according to any one of claims 1 to 6 wherein the chamber (10) has

the shape of a parallelepiped in plan view from above with parallel front and rear

walls (11, 12) inter-connected by parallel side walls (15, 16).

8. A structure according to claim 7 wherein one side wall (15) forms in a horizontal

plane, an acute angle with the front wall (11) and the other side wall (16) forms, in a

horizontal plane, a complementary obtuse angle with the front wall (11).

9 . A structure according to any one of claims 1 to 8 wherein the chamber (10) is a

closed chamber and is filled with air to a pressure greater than atmospheric pressure.

10. A structure according to claim 9 where the pressure is 0.17kPa (0.025psi).

11. A structure according to claim 9 or claim 10 wherein the inflatable members (21)

are inflated to a pressure greater than the pressure in the closed chamber (10).

12. A structure according to claim 11 wherein the pressure in the inflatable members

(21) is 5.17kPa (0.75psi).

13. A structure according to any one of claims 1 to 12 wherein at least a portion of the

cover (11, 12, 13, 14, 15, 16) is formed by an inflatable second chamber.

14. A structure according to claim 13 wherein the inflatable second chamber is

formed by two spaced sheets of flexible material (17, 18) interconnected by threads.

15. A structure according to claim 13 or claim 14 when dependent on claim 7 or any

claim appendant thereto wherein second chamber includes the front and rear walls

(11, 12) and the side walls (15,16).

16. A structure according to any one of claims 13 to 15 wherein the second chamber

incorporates the at least one inflatable member (21).

17. A structure according to any one of claims 13 to 16 when dependant on claim 10 or

any claim appendant thereto wherein the second chamber is inflated to a pressure

greater than the first-mentioned chamber.

18. A structure according to claim 17 wherein the pressure is 5.17kPa (0.75psi).

19. A structure according to claim 2 and to any claim appendant thereto wherein the

front wall (11) is covered by a protective cover (23).

20. A structure according to claim 19 wherein the protective cover comprises an

inflatable third chamber and is formed by two spaced sheet of flexible material

interconnected by threads.

21. A structure according to claim 20 wherein the third chamber is inflated to the

same pressure as the at least one inflatable member (21).

22 . A crash barrier comprising a plurality of impact absorbing structures

according to any one of claims 1 to 21 in which each cover (11, 12, 13, 14, 15, 16)

has an associated front wall (11) forming an impact surface, the structures being

placed side-by-side so that the front walls form a continuous impact surface.

23. A barrier according to claim 22 wherein the chamber is in the form of a

parallelepiped in plan view from above with front and rear walls (11, 12)

interconnected by first and second side walls (15, 16) the first side wall (15) making

an acute angle with the front wall and the structures being arranged with the first side

wall (15) of one barrier in contact with the second side wall (16) of the next adjacent

barrier.

24. A barrier according to claim 22 or claim 23 wherein the front walls ( 11 ) of

the structures are covered by a continuous protective sheet (23) extending along with

length of the barrier.