Tube-expansion energy attenuating system

1. An energy attenuating seating system for use in a vehicle compartment, comprising:

a generally horizontal seat platform adapted for vertical motion relative to the vehicle compartment;

an energy attenuating device comprising a metal tube held fixed at one end, and an oversized mandrel disposed in the tube;

a cable attached to the mandrel and extending out the other end of the metal tube, the cable supporting the seat platform in a vertical direction, wherein the front end of the seat platform is pivotally mounted to a rigid seat frame, and the cable extends from the energy attenuating device, around a pulley attached to a back end of the seat platform, and through a one-way clutch device.

2. The energy attenuating seating system of claim 1 , wherein the cable extends from the one-way clutch device to a spring-loaded retraction mechanism.

3. The energy attenuating seating system of claim 2 , wherein the energy attenuating device is part of the seat bottom, and wherein the one-way clutch and retraction mechanism are both mounted to the rigid seat frame.

4. The energy attenuating seating system of claim 3 , wherein the metal tube of the energy attenuating device comprises an expanded portion at the fixed end, and an unexpanded portion; and wherein the mandrel comprises a back end with a first diameter disposed in the expanded portion of the tube, and a front end with a second diameter smaller than the first diameter disposed in the unexpanded portion of the tube.

5. The energy attenuating seating system of claim 4 , wherein the mandrel further comprises a tapered section between the front and back ends.

6. The energy attenuating seating system of claim 5 , wherein the spring-loaded retraction mechanism applies a continuous tension to the cable with enough force to pull the cable through the one way clutch when the cable is sufficiently unloaded.

7. The energy attenuating seating system of claim 6 , wherein the spring-loaded retraction device is a take-up reel with a coil torsion spring disposed about a hub.

8. A method of attenuating the force imparted to a seated passenger in a vehicle when the vehicle is exposed to an explosive energy pulse, comprising:

providing a metal tube with an expanded portion at one end, and an unexpanded portion extending from the expanded portion to the other end;

attaching the expanded portion end of the metal tube to a rigid seat frame;

attaching a first end of a cable to an oversized mandrel disposed in the expanded portion of the tube;

extending the cable out through the other end of the metal tube;

fixing a distal portion of the cable substantially beyond the other end of the metal tube to the rigid seat frame;

supporting a moveable bottom part of the seat with a portion of the cable between the first end and the fixed distal portion;

pivotally attaching a front of the seat bottom to the rigid seat frame;

mounting the metal tube under the seat bottom with the expanded end thereof also pivotally attached to the rigid seat frame; and

extending the portion of the cable between the first end and the fixed distal portion around a pulley attached to the back end of the seat bottom, wherein the distal portion of the cable is fixed to a seat back portion of the rigid seat frame substantially above the pulley.

9. The method of claim 8 , wherein fixing the cable to the seat back portion of the rigid seat frame comprises passing the cable through a one-way clutch device attached to the seat back seat back portion of the frame.

10. The method of claim 9 , further comprising wrapping a second end of the cable around a spring loaded take-up reel.

11. The method of claim 8 , wherein the metal tube is an integral part of the seat bottom.