GB2566574A

GB2566574A - Fall arrest device

Info

Publication number: GB2566574A
Application number: GB1808532.4A
Authority: GB
Inventors: Mark Edmondson Christopher; Christopher Lawton Ian
Original assignee: Heightec Group Ltd
Current assignee: Heightec Group Ltd
Priority date: 2017-07-28
Filing date: 2018-05-24
Publication date: 2019-03-20
Anticipated expiration: 2038-05-24
Also published as: GB201712177D0; GB201808532D0; GB2566574B

Abstract

A fall arrest device comprises a body having a rope guide path for receiving a rope therein and an attachment point 7 for attaching a load thereto, wherein the action of a load being applied to the attachment point results in restraining of the rope in the rope guide path, between cams 1, 4, to arrest the movement of the device on the rope 5. A linkage member 13 is connected to the device so that it may be moved along the rope, characterised in that when the speed of said device along the rope exceeds a predetermined threshold said linkage member releases its connection with the device. Thus allowing a load to be applied to the attachment point thereby causing the rope to be restrained in the rope guide path.

Description

Fall arrest device

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.

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 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 at a point along its length and a cooperating abutment with the rope passing therebetween. When a load is applied to the body of said device 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. Alternatively the force from the harness may be applied directly to the cam again urging it toward the abutment and thereby engaging the rope. Such a device is disclosed in EP2796172.

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 moving freely down the rope to which it is attached under the action of gravity until force is applied to it 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 it to lock onto the rope. This can lead to an increased risk of injury to the user due to the distance of such fall and therefore the increased chance of collision with the structure or other objects and the sudden deceleration of the user when the device locks onto the rope. 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 the work being carried out by the user, such as painting or grit blasting etc.

In rope access or abseiling some devices do not have a free running position but continually engage the rope, the degree of engagement varying depending on the load applied to the device. When the users weight is applied to the device via a lanyard the degree of engagement is sufficient to support the users weight or arrest their fall. When the users weight is not applied to the device the degree of engagement is sufficient only to support the weight of the device. As such, this type of device may be positioned higher than the user and will remain in position until deliberately moved. Such devices are therefore equipped with a cord to allow the device to be pulled down the rope when necessary. When the user moves downwards the device is towed down by the cord, in the event of a fall the user is expected to let go of the cord allowing their weight to be applied to the device via the lanyard and the fall to be arrested. If the user fails to release the cord (as has happened in some accidents) no force is applied to the device via the lanyard and so the device does not fully engage the rope and arrest the fall. Some devices attach the towing cord via a spring clip which will detach when the force applied to it exceeds a predetermined threshold. These also have problems in that if the user applies a force below the predetermined threshold they can accelerate steadily to a high speed without releasing the cord such that they are effectively falling. This can happen when sliding down a slope such as a roof.

The invention seeks to overcome these problems by providing a fall arrest device with a towing cord which will arrest the fall when the users speed reaches a predetermined threshold.

According to the present invention there is provided a fall arrest device comprising a body having a rope guide path for receiving a rope therein and an attachment point for attaching a load thereto, wherein the action of a load being applied to the attachment point results in restraining of the rope in the rope guide path to arrest the movement of the device on the rope, said device having a linkage member in operative connection therewith, said linkage member being used to move the device along the rope, characterised in that when the speed of said device along the rope exceeds a predetermined threshold said linkage member releases its connection with said device allowing a load to be applied to the attachment point thereby causing the rope to be restrained in the rope guide path.

Preferably said linkage member comprises a flexible member such as a cord or chain.

Preferably said linkage member is also securedly affixed to the device by separate means.

Preferably said separate means is located between the attachment point and the cam pivot such that when a load is applied to it the device is urged to restrain the rope.

Preferably said linkage member is disconnected when the speed of the device along the rope exceeds a predetermined threshold.

Preferably the disconnection is triggered by centrifugal means.

Preferably said centrifugal means continue to rotate after the disconnection of the linkage member.

Preferably the linkage member may be reconnected by the user.

Preferably the force applied via the linkage member when moving the device along the rope is substantially perpendicular to the direction of movement of the engaging means when moving to the release position.

Preferably the device engages the rope sufficiently that it does not move downwards under its own weight.

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

Figure 1 is a side view of the front of the device

Figure 2 is a side view of the front of the device with the top plate removed for clarity

Figure 3 is a side view of the back of the device with the cord in the engaged position

Figure 4 is a side view of the back of the device with cover removed to show the release mechanism in the engaged position

Figure 5 is a side view of the back of the device with cover removed to show the release mechanism in the released position

Figure 6 is a rear view of the back of an alternative embodiment of the device with the cover removed

Figure 1 illustrates a fall arrest device comprising a top plate 10 mounted parallel to a base plate 6, the top plate being pivotally movable between a rope loading/removing position and a closed position to allow a rope 5 to be inserted and then retained in the device in a rope guide path defined between opposed guide surfaces of a movable cam 1 and a fixed cam 4.

The movable cam 1 is mounted on a first side of the rope guide path and the fixed cam 4 is mounted on a second side of the rope guide path. The movable cam 1 is pivotally mounted on the body of the device for pivotal movement about a pivot axis 12 extending perpendicular to the base plate 6 and perpendicular to the rope guide path. A lower end 3 of the movable cam 1 is movable to a jamming position, wherein the rope is jammed between the lower end 3 of the moveable cam 1 and the fixed cam 4 when the rope acts against the upper end 2 of the moveable cam 1, as will be described in more detail below.

A toothed wheel 8 is mounted on a shaft 16 extending through base plate 6 on a second side of the rope guide path. Wheel 8 being urged into operative contact with rope 5 by spring or similar means. On the opposite side of the base plate 6 for the rope guide path a further rotational mechanism is mounted on shaft 16 comprising a mounting disk 17 upon which is pivotally mounted a weight 18 and spring means 19 urging weight 18 into a position proximal to shaft 16. Securedly affixed to said base plate is a housing 26 covering said rotational mechanism and containing member 20 movable substantially linearly therein.

Linkage member or tether 13 is equipped with a ring like member 15 at one end. Engagement portion 24 of member 20 and housing 26 together define an aperture in which ring 15 may be engaged.

An attachment eye is defined by aperture 7 in the base plate 6 and aligned aperture 9 in top plate 10 for connecting the device to a lanyard attached to a harness of a user of the device, for example via a karabiner or similar connector inserted through the apertures 7 and 9.

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

In use, the cover plate 10 of the fall arrest device is moved to its open position and the rope 5 is inserted into the rope guide path between said rope guide surfaces of the moveable cam 1 and fixed cam 4. The cover plate is then moved to its closed position to retain the device on the rope 5. A lanyard attached to a harness of the user is attached to the attachment apertures 7, 9 of the fall arrest device.

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

The fall arrest device is prevented from moving down the rope 5 under its own weight by providing a force gripping the rope 5 by either the cam 1 or the wheel 8. When the user moves downwards the fall arrest device is towed by the user via tether 13 in its engaged position whereby it is engaged with the housing 26 and engagement portion 24 of member 20 on the first side of the rope path. The movement of the device along the rope causes wheel 8 and therefore mounting disk 17 to rotate. When the speed reaches a predetermined threshold the centrifugal force in weight 18 exceeds the centripetal force of spring 19 and said weight moves to a position radially spaced from shaft 16 as shown in figure 5. In this position weight 18 engages with abutment surface 21 of member 20 moving it laterally within housing 26. Engagement portion 24 thereby moves to a position within housing 26 opening said aperture and releasing ring 15 and thereby tether 13. After the tether is released the fall arrest device is no longer towed downwards and its movement along the rope is halted. In the case of a small amount of movement of the device along the rope after the tether has released weight 18 may then rotate further and disengage from abutment surface 21 allowing wheel 8 to continue to turn thereby preventing damage to the rope 5 by the teeth of wheel 8 being held in a fixed position.

If the user continues to move downwards load is applied via the attachment apertures 7, 9 sufficient to change the angle of the body of the device with respect to the rope 5 and causing the moveable cam 1 to rotate to lock on the rope 5, arresting movement of the rope 5 through the rope guide path and retaining the user suspended from the rope 5 by the fall arrest device.

Thereby, if the user falls due to a failure of the working equipment, or descends the working rope too quickly their movement will be arrested by the device.

If the user moves up the rope the fall arrest device can be towed upwards either by the tether or the attachment lanyard.

The tether 13 also has a restraining cord 14 connecting it to the fall arrest device on the second side of the rope path. This cord 14 prevents the tether 13 from being separated and lost when it is in the released position. Further, if the user continues to hold the tether 13 after it has been released the force applied to the fall arrest device, by virtue of being on the second side of the rope path, causes the angle of the body of the device to change arrest the movement of the rope as described above.

The tether may be moved from the released position to the engaged position by pressing the end 25 of member 20 such that it moves linearly within cover 26. Engagement portion 24 moves inside cover 26 thereby opening the aperture such that ring 15 may be inserted. When end 25 is released the spring 22 returns the engagement portion 24 to its original position closing the aperture and engaging ring

15.

In an alternative embodiment, when the speed reaches a predetermined threshold and the weight 18 moves to a position spaced from shaft 16 it engages with an abutment surface 30 formed in cover 26. This prevents further rotation of shaft 16 and wheel 8 and thereby the downward movement of the fall arrest device along the rope 5 is halted. Once the movement of the device is halted the load applied by the user to tether 13 increases as the user continues to move downwards. Tether 13 is provided with a clip 31 attached to an engaging means 32 mounted on the base plate 6 such that tether 13 and clip 31 will release from base plate 6 when the load applied to it exceeds a pre-determined threshold. Clip 31 may be in the form of a hook such that the lanyard which attaches the user to the fall arrest device may be engaged with the hook portion of the clip so that the device may be towed down the rope by the tension in the lanyard as the user climbs down or descends. Should the speed of the device reach the predetermined threshold the clip releases as described above.

As per the previous embodiment, the continued downwards movement of the user after tether 13 has released causes load to be applied via the attachment apertures 7, 9 sufficient to change the angle of the body of the device with respect to the rope 5 and causing the moveable cam 1 to rotate to lock on the rope 5, arresting movement of the rope 5 through the rope guide path and retaining the user suspended from the rope 5 by the fall arrest device.

The wheel 8 may be affixed to shaft 16 by frictional means such that wheel 8 may turn on shaft 16 when the rotational force applied to it via rope 5 exceeds a predetermined threshold. Said threshold being higher than that required to release cord 13 such that the tether 13 will release from base plate 6 before wheel 8 turns on shaft 16. In the case of a small amount of movement of the device along the rope 5 as load is applied via the attachment apertures 7, 9 the wheel 8 may turn thereby preventing damage to the rope by the teeth of the wheel being held in a fixed position.

In an alternative embodiment (not shown) the users lanyard attachment aperture or similar means may be direct to the moving cam rather than the body of the device. Such that, the application of a load via the lanyard causes the device to lock on the rope arresting the movement of the rope through the rope guide path.

In a further embodiment (not shown) the tether 13 may be connected to the lanyard attaching the user to the fall arrest device. The tether 13 is connected such that the distance between the tether/lanyard connection and the ring 15 is less than the distance from the tether/lanyard connection and the attachment apertures 7, 9.

Thereby, when the user moves downwards and applies a load to the attachment lanyard the load is transferred to the ring 15 towing the fall arrest device down the rope. When the speed exceeds the predetermined threshold and the ring 15 is released the weight of the user is then applied to the attachment apertures 7, 9 via their attachment lanyard.

In a further embodiment (not shown) the attachment apertures 7, 9 may be have a link pivotably attached proximally thereto and connecting to the engaging ring 15 or clip 31 said link providing an attachment aperture or similar for the attachment of the users lanyard proximal to said engaging ring 15 or clip 31. When the speed of the fall arrest device exceeds the predetermined threshold said clip or ring is released and the weight of the user is then applied to the attachment apertures 7, 9 through said link and via their attachment lanyard. Said link may be substantially ridged, preferably in the form of an arm or flexible, preferably in the form of a webbing sling.

Claims

1. A fall arrest device comprising a body having a rope guide path for receiving a rope therein and an attachment point for attaching a load thereto, wherein the action of a load being applied to the attachment point results in restraining of the rope in the rope guide path to arrest the movement of the device on the rope, said device having a linkage member in operative connection therewith, said linkage member being used to move the device along the rope, characterised in that when the speed of said device along the rope exceeds a predetermined threshold said linkage member releases its connection with said device allowing a load to be applied to the attachment point thereby causing the rope to be restrained in the rope guide path.

2. A fall arrest device according to claim 1 wherein said linkage member comprises a flexible member such as a cord or chain.

3. A fall arrest device according to claim 2 wherein said linkage member is configured to engage with the device.

4. A fall arrest device according to claim 2 or 3 wherein said linkage member may be connected to the lanyard attaching the user to the fall arrest device.

5. A fall arrest device according to claim 4 wherein said engagement is in the form of a hook such that the lanyard which attaches the user to the fall arrest device may be engaged with the hook so that the device may be towed down the rope by the lanyard.

6. A fall arrest device according to any preceding claim wherein said linkage member is also securedly affixed to the device by separate means.

7. A fall arrest device according to claim 6 wherein said separate means is located between the attachment point and the cam pivot such that when a load is applied to it the device is urged to restrain the rope.

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8. A fall arrest device according to claim 1 wherein the disconnection of said linkage member is triggered by centrifugal means.

9. A fall arrest device according to claim 8 wherein said centrifugal means are driven by a wheel in operative contact with the rope.

10. A fall arrest device according to claim 9 wherein said wheel is provided with teeth.

11. A fall arrest device according to claim 8 wherein said centrifugal means include a pivotally mounted weight.

12. A fall arrest device according to claim 11 wherein said centrifugal means include a spring to provide a centripetal force acting on said pivotally mounted weight.

13. A fall arrest device according to claim 11 or 12 wherein said centrifugal means include an abutment surface to engage with said weight.

14. A fall arrest device according to any preceding claim wherein said linkage member is released from operative connection with the device by the opening of an attachment aperture containing the linkage member.

15. A fall arrest device according to claim 14 wherein said opening of the attachment aperture is driven by said centrifugal means.

16. A fall arrest device according to claim 14 or 15 wherein the action of the mass engaging with the abutment surface causes said surface and the element upon which it is formed to move.

17. A fall arrest device according to claim 14, 15 or 16 wherein said centrifugal means continue to rotate after the disconnection of the linkage member.

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18. A fall arrest device according to claims 14 to 17 wherein the force applied via the linkage member when moving the device along the rope is substantially perpendicular to the direction of movement of the opening of the attachment aperture.

19. A fall arrest device according to claims 1 to 13 wherein said linkage member is released from operative connection with the device when the force applied to it exceeds a predetermined threshold.

20. A fall arrest device according to claim 19 wherein said threshold force is reached when the centrifugal means stops the device moving down the rope at said predetermined speed.

21. A fall arrest device according to claim 20 wherein the abutment surface is fixed, thereby preventing the centrifugal means from rotating when the weight engages said abutment surface.

22. A fall arrest device according to claims 19, 20 or 21 wherein said wheel will rotate after said weight engages said abutment surface when the rotational force applied to it exceeds a predetermined threshold, said threshold being higher than that required to release said linkage member such that said linkage member will release from the device before said toothed wheel rotates.

23. A fall arrest device according to any preceding claim wherein an extension is provided proximal to said attachment point to provide an attachment at the connection of the linkage member to the device said extension being pivotally mounted or otherwise flexible such that when said linkage member is released the weight of the user is applied to the attachment point via said extension.

24. A fall arrest device according to any preceding claim wherein the attachment point for the attachment of a load is direct to the moving cam wherein the action of a load being applied to the attachment point results in restraining of the rope in the rope guide path to arrest the movement of the device on the rope.

25. A fall arrest device according to any preceding claim wherein the device engages the rope sufficiently that it does not move downwards under its own weight.

26. A fall arrest device according to any preceding claim wherein, following release, the linkage member may be reconnected by the user.

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