GB2495706A

GB2495706A - A fall arrest device

Info

Publication number: GB2495706A
Application number: GB1117718.5A
Authority: GB
Inventors: Keith Jones
Original assignee: Heightec Group Ltd
Current assignee: Heightec Group Ltd
Priority date: 2011-10-13
Filing date: 2011-10-13
Publication date: 2013-04-24
Anticipated expiration: 2031-10-13
Also published as: GB2495706B; GB201117718D0; WO2013053685A2; WO2013053685A3

Abstract

A fall arrest device 2 comprising a body having a rope guide path defined between a pair of opposed rope guide surfaces 6, 8 for receiving a rope 1; a lanyard attachment for attaching a lanyard to said body, said lanyard attachment 16 being provided on a moveable member 14 moveable on said body between a first position, wherein said lanyard attachment 16 is located on a first side of said rope guide path, and a second position, wherein said lanyard attachment 16 is located on a second side of the rope guide path opposite said first side; biasing means being provided for biasing said moveable member 14 towards its first position; said moveable member 14 being urged towards its second position under the action of a load applied to the lanyard attachment 16, for example when the weight of the user is transferred to the fall arrest device 2 in the event of a fall, wherein the action of a load applied to the lanyard attachment 16 when said lanyard attachment 16 is located on said second side of the rope guide path causes rotation of the body or a moveable cam, resulting in jamming of the rope 1 in the rope guide path to arrest movement of the device on the rope 1.

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 as a back up device for arresting the descent of a person down a lifeline or secondary line in the event of failure of the person's primary working apparatus or primary working line, wherein the device is able to follow the progression of the person along the lifeline without impeding movement or requiring manual opcration of the back up device.

When working at height it is typical for a person to use a primary working apparatus, such as a descender or asccndcr, fitted to a working line to allow manual control the person's ascent or descent of the working line. For safety a lifeline or secondary line is provided, a back up device being coupled to the lifeline, whereby the back up device is adapted to automatically lock onto the lifeline in the event of failure of the primary working device or A typical back up device comprises the Petzl Shunt, such device comprising a body adapted to be fitted around a lifeline, said body being provided with a lever operated cam adapted to act against the lifeline to lock the lifeline in the body when a force is applied to the lever via a load bearing lanyard attached to the hamcss of the user in the event of a fall.

As a person moves along the working line, the back up dcvicc must be pulled along the lifeline. This is typically achieved by the usc of a separate tether cord attached the back up device whereby the person can pull the back up device along the lifeline. A separate tether cord is required because the lanyard cannot be used to pull the device without causing the device to lock onto the lifeline. In the event of an equipment failure on the working line', it is essential that the tether cord is released and that the user's load is transferred to the device via the load-bearing lanyard. Loading the device through the load-bearing lanyard in this way causes it to lock on the lifeline and arrest the fall. Failure to release the tether cord is a well known phenomena as users will often panic if their equipment fails and grab what they arc holding. Furthermore, there is a temptation for the user to deliberately attach the tether cord to their harness or to their hand to more easily pull the back up device along the lifeline. This makes normal use of the primary working equipment easier, but absolutely over-rides the ability of the back up device to lock on the lifeline by preventing the users weight from being applied to the back up device via the lanyard.

Alternative back up devices have been devised to overcome this problem, mostly using a centrifugal braking system, such as the Petzl ASAP, wherein the back up device is adapted to automatically lock onto the lifeline when the speed or acceleration of the back up device along the lifeline exceeds a predetermined level. However, such centrifugal braking systems are complex, costly and prone to damage which may not be evident in a visual inspection and thus can be unreliable.

According to a first aspect of the present invention there is provided a fall arrest device comprising a body having a rope guide path therethrough defined between a pair of opposed rope guide surfaces for receiving a rope therein; a lanyard attachment being provided for attaching a lanyard to said body, said lanyard attachment being provided on a moveable member moveable on said body between a first position, wherein said lanyard attachment is located on a first side of said rope guide path, and a second position, wherein said lanyard attachment is located on a second side of the rope guide path opposite said first side; biasing means being provided for biasing said moveable member towards its first position; said moveable member being urged towards its second position under the action of a load applied to the lanyard attachment, for example when the weight of the user is transferred to the fall arrest device in the event of a fall, wherein the action of a load applied to the lanyard attachment when said lanyard attachment is located on said second side of the rope guide path causes rotation of the body resulting injamming of the rope in the rope guide path to arrest movement of the device on the rope.

Preferably said moveable member comprises an arm pivotally mounted on the body at a pivot point located on said second side of said rope guide path, said lanyard attachment being provided on a distal end of said arm, whereby a downwards force applied to said arm, for example by means of a lanyard attached to said lanyard attachment, urges said arm towards its second position.

Preferably at least a portion of one of said guide surfaces is 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, said rotation of the body of the device resulting in movement of the movcable cam to its jamming position. In one embodiment said moveable cam may comprise an elongate member having a side surface defining one of said opposing rope guide surfaces, said elongate member being pivotally mounted on said body about a pivot axis located between opposite ends of the elongate member and extending perpendicular to said 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 lanyard attachment sufficient to move the moveable member to its second position.

Preferably said moveablc cam is provided on said fir st side of the rope guide path, said cam surfaced being defined by said lower end of the moveable cam.

Preferably said biasing means comprises a spring. The spring may be selected to ensure that lanyard aftachment remains on said first side of the rope guide path until the force applied to the lanyard connection exceeds a predetermined minimum force, indicative of the fall of a person.

Preferably the opposed rope guide surfaces are adapted to retain said device in position upon a rope located within said rope guide path in the absence of a force applied to the lanyard attachment. Such may be achieved by virtue of the spacing between the opposed rope guide surfaces, whereby 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 lanyard attachment.

This enables the device to remain above a person when the person descends a working line, minimising the fall distance of the person before the device locks onto a lifeline.

According to a further aspect of the present invention there is provided a fall arrest device comprising a body having a rope guide path defined therethrough by opposing first and second guide surfaces, at least one of said guide surfaces being provided with a cam member moveable to a jamming position against the opposing guide surface, said body being provided with a lanyard connection, said lanyard connection being adapted to be moveable between a first position on a first side of the rope guide path and a second position on a second, opposite side of the rope guide path when a load is applied to the lanyard connection, whereby the application of a load to the body through the lanyard connection when thc lanyard connection is in its sccond position causes a rotation of the body of thc device about an axis perpendicular to said rope guide path whereby the cam member is movcd to its jamming position.

According to a further aspect of the present invcntion there is provided a method of arresting the fall of a person a rope comprising providing faH arrest device having a rope guide path for passage of a rope therethrough, providing a lanyard connection on said device for connection to a lanyard secured to a harness of a person, wherein said lanyard connection is adapted to move between a first position on a first side of said rope guide path and a second position on a second side of said rope guide path, opposite said first side, when a load applied to said lanyard connection exceeds a predetermined minimum load, for example when the weight of the user is transferred to the fall arrest device in the event of a fall, the movement of the lanyard connection to said second side of the rope guide path causing rotation of the body of the device leading to jamming of the rope in the rope guide path, thus arresting the fall of the person.

Preferably said rope guide path includes a cam member, the cam member moving to a rope jamming position wherein the cam member acts against a rope passing through the rope guide path to trap the rope against a fixed member when said lanyard connection is moved to its second position due to a load applied thereto.

An embodiment 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 front view of a fall arrest device in accordance with a first embodiment of the present invention; Figure 2 is a front view of the fall arrest device of Figure 1 in a trigger configuration; and Figure 3 is a front view of the fall arrest device of Figure 1 in an arrest configuration.

A fall arrest device 2 in accordance with an embodiment of the present invention is illustrated in Figure ito 3.

The device 2 comprises a body comprising 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 I or secondary line, to he 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 earn 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 A extending perpendicular to the base plate 4 and perpendicular to the rope guide path. A lower end 10 of the moveable earn 6 is moveable to a jamming position wherein the lifeline is jamrned between the lower end 10 of the moveable cam 6 and a lower end 12 of 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 arm 14 is pivotally mounted on the body of the device, an aperture being provided at a distal end of the arm 14 to define a lanyard attachment 16 for connecting the device 2 to a lanyard attached to a harness of a user of the device 2.

The arm 14 is attached to the body at a pivot axis B located on said second side of the rope guide path, said pivot axis B extending perpendicular to both the base plate 4 and the rope guide path. The arm 14 can be moved between a first position, shown in Figure 1, wherein the lanyard attachment 16 is located on a said first side of the rope guide path in front of the lifeline 1, and a second position, shown in Figure 3, wherein the lanyard attachment 16 is located on said second side of the rope guide path behind the lifeline 1.

The arm 14 is biased towards its first position by means of a return spring, said spring having sufficient stiffness to retain the arm 14 in a position wherein the lanyard attachment 16 remains on said first side of the rope guide path during normal operation of a user's primary working equipment on a working line, permitting the device 2 to be pulled along the lifeline by the application of a pulling force to the lanyard attachment 16.

The fall arrest device 2 is intended to 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 is moved to its open position and the lifeline I is inserted into the rope guide path between said rope guide surfaces of the moveable cam 6 and fixed cam The cover plate is then moved to its closed position to retain the device on the lifeline 1. A lanyard attached to a harness of the user is attached to the lanyard attachment 16 provided at a distal end of the arm 14.

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 16, the device remains in a static position on the lifeline 1 due to the spacing between the moveable and fixed cams 6,8 applying a relatively weak restraining force on the rope.

During movement of the working equipment on the working line, the fall arrest device 2 is pulled along the lifeline 1, the return spring of the arm 14 being sufficiently stiff to allow only a small degree of rotation of the arm 14 when a pulling force is applied to the lanyard attachment 16. With this low degree of movement, the lanyard attachment 16 remains in front (relatively) of the lifeline I, on said first side of the rope guide path, as shown in Figure 1. With the lanyard attachment 16 in front of the lifeline 1, the downward force from the worker descending is applied at a position which maintains the device 2 at an angle where the moveablc cam 6 does not lock on the lifeline 1. The pulling force applied to the arm 14 via the lanyard attachment 16 is insufficient to overcome the biasing force of the return spring retaining the arm 14 in or adjacent its first position.

Where a sudden downward acceleration of the lanyard occurs, in the event of a failure of the working equipment or working line, the force applied to the arm 14 via the lanyard attachment 16 is sufficient to move the arm 14 towards its second position, causing the lanyard aftaehment 16 to move to the second side of the rope guide path, thus causing the device 2 to switch from an ascending or descending mode to an arrest mode.

In such arrest mode, the increase in force due to a sudden increase in acceleration is sufficient to overcome the stiffness of the return spring and allow further rotation of the arm 14. When the rotation of the arm 14 is such that the lanyard attachment 16 is moved behind (relatively) the lifeline I, the position at which the load is applied to the body of the device creates a moment about the rope guide path, changing the angle of the device 2 with respect to the lifeline I and causing the moveable cam 6 to rotate to lock on the lifeline 1. Thus the body of the fall arrest device 2 is rotated, under the action of the force applied to the arm 14 by the lanyard via the lanyard attachment 16, causing the lifeline to push against the upper end 11 of the moveable cam 6 to push the lower end 10 of the moveable cam 6 into its jamming position against the lifeline 1, arresting movement of the lifeline 1 through the rope guide path without damage to device or lifeline I, thus retaining the user suspended from the lifeline 1 bythe device 2.

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.

Claims

<claim-text>BClaims 1. A fall attest device comprising a body having a rope guide path therethrough defined between a pair of opposed rope guide surfaces for receiving a rope therein; a lanyard attachment being provided for attaching a lanyard to said body, said lanyard attachment being provided on a moveahie member moveable on said body between a first position, wherein said lanyard attachment is located on a first side of said rope guide path, and a second position, wherein said lanyard attachment is located on a second side of the rope guide path opposite said first side; biasing means being provided for biasing said moveable member towards its first position; said moveable member being urged towards its second position under the action of a load applied to the lanyard attachment, for example when the weight of the user is transferred to the fall arrest device in the event of a fall, wherein the action of a load applied to the lanyard attachment when said lanyard attachment is located on said second side of the rope guide path causes rotation of the body resulting in jamming of the rope in the rope guide path to arrest movement of the device on the rope.</claim-text> <claim-text>2. A fall arrest device as claimed in claim 1, wherein said moveable member comprises an arm pivotally mounted on the body at a pivot point located on said second side of said rope guide path, said lanyard attachment being provided on a distal end of said arm, whereby a downwards force applied to said arm by means of a lanyard attached to said lanyard attachment urges said arm towards its second position.</claim-text> <claim-text>3. A fall arrest device as claimed in claim 1 or claim 2, wherein at least a portion of one of said guide surfaces is 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, said mtation of the body of the device resulting in movement of the moveable cam to its jamming position.</claim-text> <claim-text>4. A fall arrest device as claimed in claim 3. wherein said moveable cam comprises an elongate member having a side surface defining one of said opposing rope guide surfaces, said elongate member being pivotally mounted on said body about a pivot axis located between opposite ends of the elongate member and extending perpendicular to said 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 lanyard attachment sufficient to move the moveable member to its second position.</claim-text> <claim-text>5. A fall arrest device as claimed in claim 4, wherein said moveable cam is provided on said first side of the rope guide path, said cam surfaced being defined by said lower end of the moveable cam.</claim-text> <claim-text>6. A fall arrest device as claimed in any of claims 3 to 5, wherein said biasing means comprises a spring.</claim-text> <claim-text>7. A fall arrest device as claimcd in claim 6, wherein said spring is selected to ensure that lanyard attachment remains on said first side of the rope guide path until the force applied to the lanyard connection exceeds a predetermined minimum force indicative of the fall of a person.</claim-text> <claim-text>8. A fall arrest device as claimed in any preceding claim, wherein said opposed rope guide surfaces are adapted to retain said device in position upon a rope located within said rope guide path in the absence of a force applied to the lanyard attachment.</claim-text> <claim-text>9. A fall arrest device as claimed in claim 8, wherein said opposed rope guide surfaces retain the device in position upon the rope by virtue of the spacing between the opposed rope guide surfaces, such that 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 lanyard attachment.</claim-text> <claim-text>10. A fall arrest device comprising a body having a rope guide path defined thcrethrough by opposing first and second guide surfaces, at least one of said guide surfaces being provided with a cam member moveable to a jamming position against the opposing guide surface, said body being provided with a lanyard connection, said lanyard connection being adapted to be moveable betwccn a first position on a first sidc of the rope guide path and a second position on a second, opposite side of the rope guide path when a load is applied to the lanyard connection, whereby thc application of a load to the body through the lanyard connection when the lanyard connection is in its second position causes a rotation of the body of the device about an axis perpendicular to said rope guide path whereby the earn member is moved to its jamming position.</claim-text> <claim-text>11. A method of arresting the fall of a person a rope cornprising providing fall arrest device having a rope guide path for passage of a rope therethrough, providing a lanyard connection on said device for connection to a lanyard secured to a harness of a person, wherein said lanyard connection is adapted to move between a first position on a first side of said rope guide path and a second position on a second side of said rope guide path, opposite said first side, when a load applied to said lanyard connection exceeds a predetermined minimum load, for example when the weight of the user is transferred to the fall arrest device in the event of a fall, the movement of the lanyard connection to said second side of the rope guide path causing rotation of the body of the device leading to jamming of the rope in the rope guide path, thus arresting the fall of the person.</claim-text> <claim-text>12. The rnethod of claim 11, wherein said rope guide path includes a cam member, the cam member rnoving to a rope jamming position wherein the cam member acts against a rope passing through the rope guide path to trap the rope against a fixed member when said lanyard connection is moved to its second position due to a load applied thereto.</claim-text> <claim-text>13. A fall arrest device substantially as herein described with reference to the accompanying drawings.</claim-text> <claim-text>14. A method of arresting the fall of a person on a rope substantially as herein described with reference to the accompanying drawings.</claim-text>