WO2013061088A2

WO2013061088A2 - Safety block and fall arrest safety line

Info

Publication number: WO2013061088A2
Application number: PCT/GB2012/052682
Authority: WO
Inventors: Owain Jones; Karl Jones
Original assignee: Latchways Plc
Priority date: 2011-10-27
Filing date: 2012-10-29
Publication date: 2013-05-02
Also published as: GB201118626D0; GB2495975B; GB2495975A; WO2013061088A3

Abstract

A safety device for use in a fall arrest system, uses a safety line drum mounted for rotation, the safety line drum being wound with a safety line comprising a kernmantle structure having a metallic inner core and an over braided protective sheath, stored substantially entirely wound onto the drum.

Description

Safetv Block and Fall Arrest Safety Line

The present invention relates to a fall arrest safety block and line. Safety blocks are known such as so called Self Retracting Lifelines (SRL). Such safety blocks include a lifeline wound onto a drum. The lifeline pays out from the drum as the user moves away from the drum, typically against a low tension re-spooler or re- winder spring mechanism, which acts to maintain a small tension in the line and retract the safety line back into the block housing as the user moves back towards the safety block. Such an arrangement is shown in, for example WO2008/139127 and WO2009/047470. Such devices frequently include speed responsive clutches (operable in response to the rotational speed of the drum reaching a threshold value) to stop the drum from paying out the wire in the event of a fall arrest event. Such devices also typically incorporate energy absorber devices to ensure that energy in arresting the fall is absorbed without being fully transmitted to the lifeline. The lifeline is typically a galvanised or stainless steel wire wound cable.

In situations where personnel are working on building roofs or ledges, there is a risk that in the event of a person falling over the building edge, the lifeline will impact upon a sharp edge or ledge of the building, in which case the life line can become severed or severely damaged.

Prior art proposals to address this issue have involved providing a rigid rubber sheath over the very end part of the lifeline (the part adjacent the connection device to the personnel safety harness). A problem with this is that the rigid sheath (and that portion of the lifeline covered by it) cannot be retracted entirely into the safety block and is therefore always exposed to the elements. Also, for safety to be realised, it is relied upon that the sheath covered end portion will be the portion impacting the building edge. If an unsheathed portion impacts the edge then the sheath is redundant.

The present invention seeks to address this issue. According to the present invention, there is provided a fall arrest safety line comprising a kernmantle structure having a metallic inner core and an over braided protective sheath.

It is preferred that the metallic inner core is a steel wire core (preferably a galvanised or stainless steel, wound wire core).

It is preferred that the over braided protective sheath is a woven over braided protective sheath. The over braided protective sheath is preferably of a para-aramid synthetic fiber or polyester synthetic fiber. For example an over braided protective sheath of a Kevlar material is suitable for use.

It is preferred that the sheath extends to cover substantially the entire length of the metallic inner core.

Beneficially, the over braided sheath is secured to the metallic inner core at opposed ends of the lifeline, typically by means of swaging. It is preferred that the metallic inner core and an over braided protective sheath are unsecured to one another along the majority of the length of the safety line. This enables relative movement to occur in the longitudinal direction of the safety line (and also preferably circumferentially) between the metallic inner core and the over braided protective sheath. This has significant performance benefits.

For this application, it is of course necessary for a safety harness connection device to be fitted at an end of the safety line.

According to a second aspect, the invention provides a safety device for use in a fall arrest system, the device comprising a safety line drum mounted for rotation, the safety line drum being wound with a safety line in accordance with the first aspect of the invention. It is preferred that the safety line is a retractable line in which the line is fully retracted into the device to be stored substantially entirely wound onto the drum.

In this realisation of the invention the device is a self retracting lifeline device having a re- spooling or rewinding mechanism, and the line is arranged to be retracted into the device to be stored substantially entirely wound onto the drum.

The use of an entire line with a protective sheath in respect of a safety block is

counterintuitive (because protection is seen as being only required at the end of the line nearest the safety harness). No prior art is known that recognises solving the edge protection problem for safety blocks in this way.

The invention will now be further described, by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a device in accordance with the invention;

Figures 2 a and 2 b are sequential diagrams showing the safety device in use; Figure 3 is a schematic sectional view of the safety line of the invention;

Figure 4 is a close up view of the safety line of the invention with a sharp edge cutting in.

Referring to the drawings, one common form of fall arrest system employs a safety block 1, as shown in Figure 1. The safety block 1 comprises a safety line or cable 2 wound around a drum 3 mounted for rotation within a casing 4. The casing 4 includes attachment means 5 for attaching the safety block to a fixed support structure (not shown). The drum 3 is biased by a tensioning and re- spooling device 6 in a direction of rotation acting to tension the safety line 2 and wind it onto the drum 3. The drum 3 is selectively connected to a brake 8 through a speed sensitive clutch 9, the speed sensitive clutch 9 being arranged to allow free rotation of the drum 3 at low speeds of rotation and to engage the drum 3 to the brake 8 at high speeds of rotation above an activation speed. The brake 8 comprises a pair of opposed friction discs 8a and 8b loaded into contact with one another, one disc 8a being fixed to the casing 4 and the other disc 8b being arranged to rotate together with the drum 3 when the clutch 9 is engaged. As shown in Figure 2, in use the safety block 1 when used on flat roofs or around roof edges can be attached to a fixed support anchor 11 structure inwardly of a region in which a user 13 to be protected is working. The user wears a personal safety harness and attaches the karabiner at the end of the safety line 2 to the harness. The user can then move around the region outwardly of the safety block, including ascending and descending any structures within the region, as necessary. As the user moves, the tensioning and spooling mechanism 6 allows the drum 3 to rotate to pay out the safety line 2 as required to allow the movement and also causes the drum 3 to rotate to reel in the safety line 2 as required so that there is no slack in the safety line 2. Normal movement of the user will result only in slow rotation of the drum 3 at speeds below the activation speed of the clutch 9. If the user falls, the safety line 2 will be pulled out and the drum 3 rotated at a rapidly accelerating speed until the speed of the drum 3 reaches the activation speed of the speed sensitive clutch 9. The speed sensitive clutch 8 will then engage the drum 3 with the brake 8. The energy of the user's fall is then absorbed by friction in the brake 8 until the fall is arrested, and rotation of the drum 3 is stopped. As an alternative to a friction brake safety blocks can be fitted with other forma of energy absorber, such as plastically deformable metallic strips that deploy and plastically deform to absorb energy. In figure 2A the user can be seen walking close to the edge 15 of the roof 16 of a building 17. The safety line 2 is paying out of the safety block 1. In figure 2B it can be seen that the user 13 has fallen over the edge 15 of the building and is suspended in mid air 9the fall arrest block having done its job of arresting the fall). However as can be seen in figure 2B the sharp edge 15 of the building is cutting into the safety line 2. The risk is with standard lifelines of bare wound galvanised or stainless steel wire that the life line can become severed or severely damaged, possibly resulting in fatality. In accordance with the invention, the safety line 2 used for the safety block device and wound on the drum is a kernmantle structure having a metallic inner core 20 and an over braided protective sheath 21. Typically, as shown in figure 3, the metallic inner core 20 is a galvanised or stainless steel wound wire structure having the outer protective sheath 21 over braided. The protective sheath 21 is designed to protect the interior wire core from being damaged when a sharp structure (such as a sharp building edge) cuts into the safety line 2. Suitable materials are, for example woven over braided protective sheath of a para- aramid synthetic fiber (such as Kevlar RTM) or polyester synthetic fiber. The over braided sheath 21 is secured to the metallic inner core 20 at opposed ends of the lifeline typically by means of swaging, but importantly the metallic inner core 20 and the over braided protective sheath 21 are unsecured to one another along the majority of the length of the safety line. This enables relative movement to occur in the longitudinal direction of the safety line 2 (and also preferably circumferentially) between the metallic inner core 20 and the over braided protective sheath 21. As shown in figure 4 this has a significant performance benefit in that when the safety line swings into contact with the sharp edge 15, relative movement between the inner core 20 and the over braided protective sheath 21 enables the sheath to 'ruck up' slightly (arrow A in figure 4), absorbing energy and protecting the inner core 2 from a knife edge biting cut. Effectively the interior metallic core is permitted to stretch or slip (Arrow B in figure 4) without being snagged on the sharp edge 15 of the building which is also cushioned by the 'rucked up' sheath 21.

An important feature of the arrangement is that substantially the entire length of the safety line 2 with the protective sheath over braided can be wound on to the drum right up to the karabiner connection end of the safety line 2. This means that when retracted and not in use, none of the safety line is exposed out of the safety block device 1.

Claims

A safety device (such as a safety block) for use in a fall arrest system, the device comprising a safety line drum mounted for rotation, the safety line drum being wound with a safety line comprising a kernmantle structure having a metallic inner core and an over braided protective sheath, stored substantially entirely wound onto the drum.

A safety device according to claim 1, comprising a retractable safety line in which the line is fully retracted into the device to be stored substantially entirely wound onto the drum.

A safety device according to claim 2, wherein the device is a self retracting lifeline device having a re- spooling or rewinding mechanism, and the line is arranged to be retracted into the device to be stored substantially entirely wound onto the drum.

A fall arrest safety line comprising a kernmantle structure having a metallic inner core and an over braided protective sheath.

A safety line or device according to any preceding claim wherein the metallic inner core is a steel wire core (preferably a galvanised stainless steel wound wire core).

A safety line or device according to any preceding claim, wherein the over braided protective sheath is a woven over braided protective sheath.

A safety line or device according to any preceding claim, wherein the sheath extends to cover substantially the entire length of the metallic inner core.

A safety line or device according to any preceding claim, wherein the over braided protective sheath is of a para-aramid synthetic fiber or polyester synthetic fiber.

9. A safety line or device according to any preceding claim having a safety harness connection device fitted at an end thereof.

10. A safety line or device according to any preceding claim, wherein the over

braided sheath is secured to the metallic inner core at opposed ends of the lifeline.

11. A safety line or device according to claim 10, wherein the over braided sheath is secured to the metallic inner core at opposed ends of the lifeline by means of swaging.

12. A safety line or device according to any preceding claim wherein the metallic inner core and an over braided protective sheath are unsecured to one another along the majority of the length of the safety line.

13. A fall arrest safety line comprising an inner wire wound metallic core and an outer protective sheath extending along substantially the entire length of the safety line, wherein the sheath is secured to the metallic inner core at opposed ends of the lifeline and the metallic inner core and an over braided protective sheath are unsecured to one another along the majority of the length of the safety line.