Energy absorbing apparatus
Described herein are energy absorbing apparatuses and methods of their use that utilize varying energy absorbing relationships between the apparatus members to absorb an energy input. The energy absorbing process occurs via a material forming process.
1. A self-retracting lifeline device, comprising:
a line having a first end that extends and retracts from the self-retracting lifeline device, and an opposing end of the line coupled to at least one energy absorbing member,
wherein, when the first end of the line extends from the self-retracting lifeline device at a rate below a predefined threshold, the first end of the line is free to move relative to the at least one energy absorbing member, and when the first end of the line extends from the self-retracting lifeline device at a rate beyond the predefined threshold, the at least one energy absorbing member engages the line and applies a retarding force on the rate of extension of the line, transferring kinetic energy from the line into work energy by wire drawing of the at least one energy absorbing member, such that a wire is plastically deformed to a reduced diameter during the wire drawing by pulling the wire through a reduced diameter member having a narrowing waist or shoulder.
2. The self-retracting lifeline device as claimed in claim 1 wherein the retarding force results in a halt in movement of the first end of the line.
3. The self-retracting lifeline device as claimed in claim 1 wherein an external force imposes motion to the first end of the line.
4. The self-retracting lifeline device as claimed in claim 1 wherein the first end of the line moves in a linear direction and the retarding force applied to the first end of the line is a linear force.
5. The self-retracting lifeline device as claimed in claim 1 wherein the first end of the line rotates and the retarding force applied to the first end of the line applies a torque to the first end of the line.
6. The self-retracting lifeline device as claimed in claim 1 wherein the retarding force is applied in a direction substantially opposite a direction of travel of the first end of the line.
7. The self-retracting lifeline device as claimed in claim 1 wherein a rate at which kinetic energy is absorbed by the at least one energy absorbing member is related to:
a force or torque applied to the at least one energy absorbing member by the line; and/or
a distance traveled or rotated by the first end of the line.
8. The self-retracting lifeline device as claimed in claim 1 wherein the at least one energy absorbing member has substantially uniform material characteristics resulting in a substantially linear retarding force being applied to the first end of the line.
9. The self-retracting lifeline device as claimed in claim 1 wherein the at least one energy absorbing member has non-uniform material characteristics resulting in a non-linear retarding force being applied to the first end of the line.
10. The self-retracting lifeline device as claimed in claim 9 wherein the material characteristics are varied along part or all of a length of the at least one energy absorbing member and the material characteristics are selected from a group consisting of: wire diameter, wire composition, wire material treatments prior to forming, and combinations thereof.
11. The self-retracting lifeline device as claimed in claim 1 wherein the at least one energy absorbing member is made of lead or a lead alloy.
12. The self-retracting lifeline device as claimed in claim 1 wherein the at least one energy absorbing member includes a bulged element that passes through a confined volume relative to the extrudable material shape and size.
13. The self-retracting lifeline device as claimed in claim 12 wherein the bulged element is enclosed within a housing and when relative movement occurs between the at least one energy absorbing member and the housing, the bulged element is forced into a more confined region of the housing.
14. The self-retracting lifeline device as claimed in claim 1 wherein a rate at which the retarding force is applied to the first end of the line is substantially uniform.
15. The self-retracting lifeline device as claimed in claim 1 wherein a rate at which the retarding force is applied to the first end of the line is non-uniform, the non-uniform rate achieved by varying materials used and a rate of movement of the first end of the line.
16. A method of absorbing energy using a self-retracting lifeline device comprising:
a line having a first end that extends and retracts from the self-retracting lifeline device, and an opposing end of the line coupled to at least one energy absorbing member,
wherein, when the first end of the line extends from the self-retracting lifeline device at a rate below a predefined threshold, the first end of the line is free to move relative to the at least one energy absorbing member, and when the first end of the line extends from the self-retracting lifeline device at a rate beyond the predefined threshold, the at least one energy absorbing member engages the line and applies a retarding force on the rate of extension of the line, transferring kinetic energy from the line into work energy by wire drawing of the at least one energy absorbing member,
the method comprising:
applying a motion causing energy input on the first end of the line that exceeds the predefined threshold thereby triggering the at least one energy absorbing member to absorb at least part of a kinetic energy of the first end of the line by a wire drawing process, such that a wire is plastically deformed to a reduced diameter during the wire drawing by pulling the wire through a reduced diameter member having a narrowing waist or shoulder.