GB2517675A

GB2517675A - Fall arrest device and a restraining device therefor

Info

Publication number: GB2517675A
Application number: GB1309605.2A
Authority: GB
Inventors: Keith Jones
Original assignee: Heightec Group Ltd
Current assignee: Heightec Group Ltd
Priority date: 2013-05-29
Filing date: 2013-05-29
Publication date: 2015-03-04
Also published as: GB201309605D0

Abstract

A fall arrest device 2 comprises a base plate 4 and a cover plate (omitted for clarity) mounted parallel to the base plate 4, the cover plate is pivotally movable between a rope loading/removing position and a closed position to allow a rope 1, to be inserted and then retained in the device 2 in guide path between opposed guide surfaces of a pivotable cam 6 and a fixed cam 8. An attachment eye 14 is defined by aligned apertures in the base plate 4 and cover plate connecting the device 2 to a lanyard attached to a harness of a user of the device 2. A restraining device 20 is connected above the fall arrest device by means of a tether 26 and has a rope guide path defined between a fixed abutment 22 and a moveable abutment 24, the moveable abutment 24 being biased towards the fixed abutment 22 by means of a spring 6 to exert a gripping force on the lifeline 1.

Description

Fall Arrest Device and a Restraining Device Therefor This invention relates to a fall arrest device arresting the descent of a person or other load down a rope, lifeline, cable, web or other similar elongate load supporting member or line (collectively referred to hereinafter as" rope"), and in particular to a fall arrest device for use for arresting the descent of a person down a rope in the event of a fall, and to a restraining device for a fall arrest device.

When working at height it is typical for a person to use a fall arrest device being coupled to a rope, whereby the device is adapted to automatically lock onto the rope in the event of a fall.

Such fall arrest devices connect to the safety harness of the user, typically via a lanyard, and freely travel up and down the rope, engaging the rope when the force applied to them via the harness exceeds a predetermined threshold (i.e. when the user slips or falls). Such devices commonly contain a cam pivotally mounted on the body of the device and a cooperating abutment with the rope passing therebetween.

In one known design, when a load is applied to the body of said device via an attachment point on the body, the rope comes into operative contact with the distal end of the cam, urging the proximal end of the cam toward the abutment, thereby engaging the rope therebetween. In an alternative design, the attachment point for the harness is provided on the distal end of the cam such that a load applied to the attachment point urges the proximal end of the cam toward the abutment, thereby engaging the rope therebetween.

A problem with such known fall arrest devices is that the device tends to rest below the user when in its free running position, the device freely moving down the rope to which it is attached under the action of gravity until it is arrested by a lanyard attached to a harness worn by the user. In the event of a fall, the user can fall through a distance equivalent to twice the length of the lanyard before a load is applied to the device causing the device to lock onto the lifeline. This can lead to an increased risk of injury to the user due to the distance of such fall and the sudden deceleration of the user when the device locks onto the lifeline. If the lanyard is shortened to reduce this risk, the device tends to get in the way of the user and can be damaged by work being carried out by the user, such as painting, grip blasting etc. According to a first aspect of the present invention there is provided a fall arrest device comprising a first body having a first rope guide path for receiving a rope therein and an attachment point for attaching a load thereto, wherein the action of a load applied to the attachment point results in restraining of the rope in the first rope guide path to arrest movement of the device on the rope, said device further comprising a second body having a second rope guide path defined between a pair of opposed rope guide surfaces for receiving said rope therein at a location above said first rope guide path, said opposed rope guide surfaces of the second rope guide path being adapted to retain said device in position until the load applied to the attachment point exceeds a predetermined limit.

Preferably said second body is linked to said first body by a linkage member.

Preferably said linkage member is directly or indirectly coupled to said attachment point.

In one embodiment said attachment point is located on a first side of said first rope guide path, said linkage member being coupled to said first body on said first side of said first rope guide path.

Said linkage member comprises a flexible member, such as a rope or chain.

Alternatively the linkage member may comprise a rigid link, said linkage member being pivotally coupled to said first body.

At least a portion of said linkage member may be formed from an elastic material.

In one embodiment the linkage member may be adapted such that the second body becomes detached from the first body when the load applied to the attachment point exceeds a predetermined level.

Preferably said opposed rope guide surfaces of the second rope guide path retain the device in position upon the rope by virtue of the spacing between the opposed rope guide surfaces, such that, in use, the rope guide surfaces engage the rope with sufficient force to retain the device in position on the rope in the absence of any force applied to the attachment point. Preferably said at least one of said opposed rope guide surfaces of the second rope guide path is biased towards the other to apply a compressive force against the rope passing therebetween. A first of said opposed rope guide surfaces of the second rope guide path may arranged to be urged away from a second of said opposed rope guide surfaces when a load is applied to the attachment point.

In one embodiment said first rope guide surface may be arranged to be urged away from said second guide surface when a load is applied to said linkage member via said attachment point.

Said first rope guide path may be defined between a pair of opposed rope guide surfaces for receiving a rope therebetween, at least a portion of one of said guide surfaces of the first rope guide path being defined by a face of a moveable cam, adapted to be moveable into a rope jamming position, wherein the rope is pressed between the moveable cam and the opposing rope guide surface to arrest movement of the rope through the rope guide path.

In one embodiment said moveable cam may comprise an elongate member having a side surface defining one of said opposing rope guide surfaces of the first rope guide path, one end of said elongate member defining a cam surface moveable into said jamming position when the rope acts against a second opposite end of the elongate member when the device is rotated by virtue of a load applied to the attachment point.

In an alternative embodiment said attachment point may be provided on a distal end of said elongate member, whereby a second end of said elongate member defines a cam surface moveable into said jamming position when by virtue of a load applied to the attachment point.

According to a further aspect of the present invention there is provided a restraining device for a fall arrest device, said restraining device comprising a body having a rope guide path defined between a pair of opposed rope guide surfaces for receiving said rope therein at a location above said fall arrest device, a linkage member being provided on said body, a distal end of said linkage member being adapted to be connected to said tall arrest device at or adjacent an attachment point thereof, said opposed rope guide surfaces of the rope guide path being adapted to retain said restraining device in position on the rope until a load applied to the linkage member via the fall arrest device exceeds a predetermined limit. Preferably said distal end of the linkage member is provided with a connector for attaching the linkage member to an attachment point of a fall arrest device.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a schematic view of a fall arrest device in accordance with a first embodiment of the present invention; and Figure 2 is a schematic view of a fall arrest device in accordance with a second embodiment of the present invention.

Figure 1 illustrates a tall arrest device 2 incorporating a restraining device 20 in accordance with an embodiment of the present invention. The fall arrest device 2 comprises a base plate 4 and a cover plate (omitted for clarity) mounted parallel to the base plate 4, the cover plate being pivotally movable between a rope loading/removing position and a closed position to allow a rope, such as a lifeline 1 or secondary line, to be inserted and then retained in the device 2 in a rope guide path defined between opposed guide surfaces of a moveable cam 6 and a fixed cam 8.

The moveable cam 6 is mounted on a first side of the rope guide path and the fixed cam 8 is mounted on a second side of the rope guide path. The moveable cam 6 is pivotally mounted on the body of the device for pivotal movement about a pivot axis extending perpendicular to the base plate 4 and perpendicular to the rope guide path. A lower end 10 of the moveable cam 6 is moveable to a jamming position, wherein the lifeline is jammed between the lower end 10 of the moveable cam 6 and the fixed cam 8, when the lifeline acts against the upper end 11 of the moveable cam 6, as will be described in more detail below.

An attachment eye 14 is defined by aligned apertures in the base plate 4 and cover plate connecting the device 2 to a lanyard attached to a harness of a user of the device 2, for example via a karabiner or similar connector inserted through the attachment eye 14.

The restraining device 20 is in the form of a second body having a rope guide path defined between a fixed abutment 22 and a moveable abutment 24, the moveable abutment 24 being biased towards the fixed abutment 22 by means of a spring 26 to exert a gripping force on the lifeline 1 located in said rope guide path. The restraining device 20 is adapted to be fitted to the lifeline 1 at a position above the fall arrest device 2. The restraining device 20 may have a releasable cover member (not shown) or similar opening to allow it to be attached to and removed from the lifeline 1.

The restraining device 20 is connected to the fall arrest device 2 via a flexible tether 26. The tether is connected at a first end to an attachment eye 28 provided on the body of the restraining device and is connected at a second end, either directly or indirectly, to the attachment eye 14 of the fall arrest device 2. As such the restraining device 20 serves to retain the fall arrest device 2 in place on the lifeline 1 in the absence of a force on the tether 26.

In an alternative embodiment, the tether 26 may be operatively coupled to the moveable abutment 24 of the restraining member 20 at its first end, such that, when a load is applied to the attachment eye, the tether urges the moveable abutment of the restraining member away from the fixed abutment.

The fall arrest device 2 may be used as a back up device on a lifeline to arrest the fall of a person should the working equipment, such as an ascender or descender, attached to a working line fail.

In use, the cover plate of the fall arrest device 2 is moved to its open position and the lifeline 1 is inserted into the rope guide path between said rope guide surfaces of the moveable cam 6 and fixed cam 8. The cover plate is then moved to its closed position to retain the device on the lifeline 1. The restraining device 20 is attached to the lifeline 1 at a position above the fall arrest device 2. A lanyard attached to a harness of the user is attached to the lanyard attachment 14 of the fall arrest device 2.

During normal use of the working equipment on the working line, the weight of the user is supported by the working equipment.

With no pull on the lanyard attachment 14, the fall arrest device 2 remains in a static position on the lifeline 1 due to the action of the restraining device 20 on the lifeline 1, the fall arrest device 2 being held in place via the tether 26.

During movement of the working equipment on the working line, a downward force applied to the fall arrest device 2 via the attachment eye 14 is transferred to the restraining device 2 via the tether 26, overcoming the frictional restraining force of the moveable abutment 24 on the lifeline 1 (or pulling the moveable abutment away from the fixed abutment and releasing the grip of the restraining member on the lifeline), allowing the fall arrest device 2 to move down the lifeline 1.

Where a sudden downward acceleration is applied to the attachment eye 14 of the fall arrest device 2, in the event of a fall due to a failure of the working equipment or working line, the force applied to attachment eye 14 is sufficient to change the angle of the first body of the device 2 with respect to the lifeline 1 and causing the moveable cam 6 to rotate to lock on the lifeline 1, arresting movement of the lifeline 1 through the rope guide path and retaining the user suspended from the lifeline 1 by the fall arrest device device 2.

In a second embodiment, shown in Figure 2, the attachment eye 114 for attachment of a harness to the fall arrest device 102 is provided on a distal end 111 of the moveable cam 106 so that a load applied to the attachment eye 114 urges the lower end 110 of the moveable cam 106 into its jamming position against the lifeline 1, against the restoring force of a return spring (not shown), as is known in the art. In such embodiment, the tether 126 connecting the restraining device 120 to the fall arrest device 102 may be coupled to the attachment eye 114 provided on the distal end 111 of the moveable cam 106 (or to an adjacent point on the moveable cam 106).

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention. In an alternative embodiment the tether connecting the restraining member to the first body of the device may be formed from or incorporate an elastic material, such as an elastic cord or spring, to ensure that the restraining member does not interfere with the operation of the moveable cam. Alternatively the tether may be arranged to detach from the restraining member of first body of the device a sudden force is applied to the attachment eye.

Claims

Claims 1. A fall arrest device comprising a first body having a first rope guide path for receiving a rope therein and an attachment point for attaching a load thereto, wherein the action of a load applied to the attachment point results in restraining of the rope in the first rope guide path to arrest movement of the device on the rope, said device further comprising a second body having a second rope guide path defined between a pair of opposed rope guide surfaces for receiving said rope therein at a location above said first rope guide path, said opposed rope guide surfaces of the second rope guide path being adapted to retain said device in position until the load applied to the attachment point exceeds a predetermined limit.
2. A device as claimed in claim 1, wherein said second body is linked to said first body by a linkage member.
3. A device as claimed in claim 2, wherein said linkage member is directly or indirectly coupled to said attachment point.
4. A device as claimed in claim 2 or claim 3, wherein said attachment point is located on a first side of said first rope guide path, said linkage member being coupled to said first body on said first side of said first rope guide path.
5. A device as claimed in any of claims 2 to 4, wherein said linkage member comprises a flexible member, such as a rope or chain.
6. A device as claimed in any of claims 2 to 4, wherein said linkage member comprises a rigid link, said linkage member being pivotally coupled to said first body.
7. A device as claimed in any of claims 2 to 6, wherein at least a portion of said linkage member is formed from an elastic material.
8. A device as claimed in any of claims 2 to 7, wherein the linkage member is adapted such that the second body becomes detached from the first body when the load applied to the attachment point exceeds a predetermined level.
9. A fall arrest device as claimed in any preceding claim, wherein said opposed rope guide surfaces of the second rope guide path retain the device in position upon the rope by virtue of the spacing between the opposed rope guide surfaces, such that, in use, the rope guide surfaces engage the rope with sufficient force to retain the device in position on the rope in the absence of any force applied to the attachment point.
10. A device as claimed in claim 9, wherein said at least one of said opposed rope guide surfaces of the second rope guide path is biased towards the other to apply a compressive force against the rope passing therebetween.
11. A device as claimed in claim 10, wherein a first of said opposed rope guide surfaces of the second rope guide path is arranged to be urged away from a second of said opposed rope guide surfaces when a load is applied to the attachment point.
12. A device as claimed in claim 11, wherein said first rope guide surface is arranged to be urged away from said second guide surface when a load is applied to said linkage member via said attachment point.
13. A fall arrest device as claimed in any preceding claim, wherein said first rope guide path is defined between a pair of opposed rope guide surfaces for receiving a rope therebetween, at least a portion of one of said guide surfaces of the first rope guide path being defined by a face of a moveable cam, adapted to be moveable into a rope jamming position, wherein the rope is pressed between the moveable cam and the opposing rope guide surface to arrest movement of the rope through the ropeguidepath.
14. A device as claimed in claim 13, wherein said moveable cam comprises an elongate member having a side surface defining one of said opposing rope guide surfaces of the first rope guide path, one end of said elongate member defining a cam surface moveable into said jamming position when the rope acts against a second opposite end of the elongate member when the device is rotated by virtue of a load applied to the attachment point.
15. A device as claimed in claim 13, wherein said attachment point is provided on a distal end of said elongate member, whereby a second end of said elongate member defines a cam surface moveable into said jamming position when by virtue of a load applied to the attachment point.
16. A restraining device for a fall arrest device, said restraining device comprising a body having a rope guide path defined between a pair of opposed rope guide surfaces for receiving said rope therein at a location above said fall arrest device, a linkage member being provided on said body, a distal end of said linkage member being adapted to be connected to said fall arrest device at or adjacent an attachment point thereof, said opposed rope guide surfaces of the rope guide path being adapted to retain said restraining device in position on the rope until a load applied to the linkage member via the fall arrest device exceeds a predetermined limit.
17. A restraining device as claimed in claim 16, wherein said distal end of the linkage member is provided with a connector for attaching the linkage member to an attachment point of a fall arrest device.
18. A fall arrest device substantially as herein described with reference to the accompanying drawings.