Collapsible support

1. A collapsible support for absorbing energy during an impact, the collapsible support comprising:

a hollow tubular body made of a plastic material that extends along a longitudinal axis, the tubular body having a first end wall, a second end wall, and at least one side wall that extends around the axis and between said wall ends, the at least one side wall having at least two sections, adjacent sections of the aide wall being separated by a step in the cross-section of said side wall when viewed in a plane parallel to said axis, and wherein the end walls and at least one side wall enclose a hollow volume, and

wherein the step in the at least one side wall is a step in both an outer surface of said wall and an inner surface of said wall, and

wherein a vent aperture is disposed in one of the side walls, and

wherein the tubular body is adapted to deform so that sections of wall collapse with one section moving inside another section upon the application of a compressive force applied to said body along said axis.

2. The collapsible support as claimed in claim 1 , wherein the tubular body is generally square or rectangular as viewed in a cross-section transverse to the longitudinal axis.

3. The support as claimed in claim 2 , wherein the at least one side wall forms a stepped pyramid.

4. The collapsible support as claimed in claim 1 , wherein the tubular body is generally circular or oval as viewed in a cross-section transverse to the longitudinal axis.

5. The collapsible support as claimed in claim 1 , wherein the at least one side wall includes a vent aperture by which air inside the hollow volume may escape when the tubular body deforms.

6. The collapsible support as claimed in claim 1 , wherein a force required to collapse the support is less than 10 kN.

7. The collapsible support as claimed in claim 6 , wherein the force required to collapse the support is less than 7 kN.

8. The collapsible support as claimed in claim 1 , wherein the support is made from a blow molded plastics material.

9. An apparatus for absorbing the energy of an impact of a moving body, comprising:

a knee bolster for receiving the impact of said moving body;

a rigid support structure; and

at toast one collapsible support between the knee bolster and the support structure arranged to collapse and absorb energy upon contact of said moving body on the knee bolster; and

wherein said collapsible support includes a first and second end wall that defines a hollow volume and extends along the longitudinal axis between the support structure and the knee bolster, arid is made of a plastic material.

10. The apparatus as claimed in claim 9 , wherein the at least one collapsible support includes a side wall and wherein the side wall tapers towards the longitudinal axis from the support structure to the knee bolster.

11. The apparatus as claimed in claim 9 , wherein the collapsible support is joined to the knee bolster by the first end wall.

12. The apparatus as claimed in claim 11 , wherein the second end wall includes a threaded metal insert for a screw by which the knee bolster is joined to the collapsible support.

13. The apparatus as claimed in claim 9 , wherein the knee bolster is joined to the support structure by at least two spaced-apart collapsible supports that are connected by a cross-beam that extends across the knee bolster.

14. The apparatus as claimed in claim 9 , wherein the collapsible support is joined to the support structure by the second end wall.

15. The apparatus as claimed in claim 14 , wherein the first end wall has a fastening boss that engages with a recess in the support structure when the collapsible support is joined to the support structure.

16. The apparatus as claimed in claim 15 , wherein the cylindrical protrusion has a threaded bare for a screw by which the support structure is joined to the collapsible support.