Safety device
A safety device for a fall arrest system comprises: a body, attachment means for attaching the safety device to a support structure, a drum mounted for rotation relative to the body, a safety line wound on the drum, a speed sensitive clutch connected to the drum, and a linear energy absorber connecting the body to the attachment means, in which the speed sensitive clutch is adapted to respond to rotation of the drum relative to the body in a direction tending to unwind the safety line from the drum and above a predetermined speed by locking the drum against further rotation in said direction relative to the body, and the linear energy absorber is adapted to respond, when the speed sensitive clutch has locked the drum, to an applied load along the safety line greater than a threshold value by deploying and absorbing energy so that the attachment means moves away from the body.
1. A safety device suitable for use in a fall arrest system, and comprising:
a body, attachment means for attaching the safety device to a support structure, a drum mounted for rotation relative to the body, a safety line wound on the drum, a speed sensitive clutch connected to the drum, and a linear energy absorber connecting the body to the attachment means, in which the speed sensitive clutch is adapted to respond to rotation of the drum relative to the body in a direction tending to unwind the safety line from the drum and above a predetermined speed by locking the drum against further rotation in said direction relative to the body, and the linear energy absorber is adapted to respond, when the speed sensitive clutch has locked the drum, to an applied load along the safety line greater than a threshold value by deploying and absorbing energy so that the attachment means moves away from the body.
2. A safety device according to claim 1 , in which the linear energy absorber comprises a plastically deformable element which is plastically deformed to absorb energy when the linear energy absorber deploys.
3. A safety device according to claim 2 , in which the plastically deformable element is an elongate member which is plastically deformed by passing through a deforming means when the linear energy absorber deploys.
4. A safety device according to claim 3 , in which the elongate member is a strip or a round bar.
5. A safety device according to claim 3 , in which the elongate member is stainless steel.
6. A safety device according to claim 1 , in which the linear energy absorber comprises multiple layers of fabric linked by stitches, the layers of fabric being separated and the stitches torn out to absorb energy when the linear energy absorber deploys.
7. A safety device according to claim 1 , in which the linear energy absorber is modular and can be removed and replaced from the safety device as a single element.
8. A safety device according to claim 1 , in which the body includes a frame acting as a load path between the drum and the linear energy absorber, and the drum and linear energy absorber are located within the frame.
9. A safety device according to claim 1 , in which the speed sensitive clutch is arranged so that when the drum has been locked the load on the safety line must be reduced to zero to unlock the drum.
10. A safety device according to claim 9 , in which the speed sensitive clutch is arranged so that when the drum has been locked the drum must be rotated by the rewinding means in a direction tending to wind the safety line onto the drum in order to unlock the drum.
11. A safety device according to claim 1 , and further comprising a rewinding means adapted to bias the drum to rotate relative to the body in a direction tending to wind the safety line onto the drum.