Latch activation between members
Described herein is a system, method of use and Self Retracting Lifeline (SRL) apparatus using a system that governs a dynamic response between members causing a halt in relative motion between the members. Magnetic interactions, eddy current drag forces and centrifugal and/or inertial forces may provide various mechanisms of governing movement.
1. A method of controlling a self-retracting lifeline including a coupler configured to selectively couple a spool having a line thereon to a latch on an external member, and in doing so slow or halt relative motion between the spool and the external member, wherein the coupler includes a pawl linked to and rotating with the spool when the line is withdrawn from the spool, the method comprising:
applying a force to the line causing withdrawal of the line from the spool;
wherein when the spool rotates, due to line withdrawal from the spool, below a velocity and acceleration threshold, the pawl oscillates radially outward and inward relative to an axis of rotation of the spool and the coupler does not couple the spool to the external member; and
wherein when the spool rotates, due to line withdrawal from the spool, above the velocity and acceleration threshold, the pawl moves radially outward to a deployed position such that the pawl or a part thereof engages the latch, thereby coupling the external member to the spool and in doing so halting relative motion between the external member and the spool.
2. The method of claim 1 wherein the pawl is directly linked to the spool.
3. The method of claim 1 wherein the pawl is indirectly linked to the spool.
4. The method of claim 1 wherein the pawl is biased to an uncoupled position.
5. The method of claim 4 wherein the bias is provided by a spring.
6. The method of claim 1 wherein the coupler comprises two pawls, both pawls rotating with the spool.
7. The method of claim 1 wherein the latch comprises a tooth.
8. The method of claim 7 wherein the external member comprises at least two teeth.
9. The method of claim 1 wherein a distal end of the pawl engages the latch.
10. The method of claim 1 where in the latch includes a ratchet so that once coupled, the spool can only move in a reverse direction to wind line onto the spool and line cannot be drawn from the spool.
11. The method of claim 1 wherein a pawl velocity sensitivity is tuned to permit oscillation by balancing a centrifugal force imposed on the pawl to move outwards with an opposite bias force moving the pawl inwards.
12. The method of claim 1 where in a pawl acceleration sensitivity is tuned by balancing a pawl inertia to movement caused by a centrifugal force outward against a rate of change in spool rotation.
13. The method of claim 1 wherein the external member is a housing around the spool or a part thereof.
14. The method of claim 1 wherein the spool rotates within the external member.
15. The method of claim 1 wherein the pawl has an axis of rotation, the axis of rotation of the pawl offset from the axis of rotation of the spool.
16. The method of claim 1 wherein the pawl is an elongated member with a first end linked to the spool and an opposing second end, on coupling, latching with the external member.
17. The method of claim 16 wherein the pawl at the first end is indirectly linked to the spool.
18. The method of claim 1 wherein the pawl remains coupled to the external member while spool velocity and acceleration remain above the velocity and acceleration threshold, and decoupling occurs when the spool velocity and acceleration lowers below the velocity and acceleration threshold.
19. The method of claim 1 wherein the external member is a peripheral energy absorber that slows or halts relative motion between the spool and external member.
20. The method of claim 1 wherein the halting of relative motion between the external member and spool results in zero absolute velocity of the spool and line withdrawal from the spool.