Improved Fall Arrest System for a Person Climbing a Ladder

Abstract

A fall-arrest system for a person climbing a ladder (7) affixed to or supported by a structure, comprises: an elongate track securable to the ladder (7) so as to lie adjacent to the intended route of a person climbing or descending the ladder; a sliding device (13) which in use is coupled to the elongate track and configured to be freely displaceable therealong when the person is climbing the ladder; and a safety line (12) extending from the sliding device (13) for attachment to a harness attachment point of a safety harness worn by the person climbing or descending the ladder, the sliding device (13) incorporating a locking mechanism configured to allow the sliding device (13) to freely slide along the elongate track during normal movement of the person connected thereto by the safety line and to automatically lock the sliding device (13) to the elongate track in the event of the person falling from said ladder. The fall-arrest system is characterised in that the elongate track comprises a flexible belt (8) configured to depend from an upper end of the ladder.

Claims

1. A fall-arrest system for a person climbing a ladder affixed to or supported by a structure, comprising: an elongate track securable to the ladder so as to lie adjacent to the intended route of a person climbing or descending the ladder; a sliding device which in use is coupled to the elongate track and configured to be freely displaceable therealong when the person is climbing the ladder; a safety line extending from the sliding device for attachment to a harness attachment point of a safety harness worn by the person climbing or descending the ladder, the sliding device incorporating a locking mechanism configured to allow the sliding device to freely slide along the elongate track during normal movement of the person connected thereto by the safety line and to automatically lock the sliding device to the elongate track in the event of the person falling from said ladder; wherein the elongate track comprises a flexible belt configured to depend from an upper end of the ladder.

2. A fall-arrest system according to claim 1, wherein the sliding device comprises a first part engaging the flexible belt and a second part coupled to the safety line, with the second part configured to move relative to the first part from a first position to a second position to activate the locking mechanism in order to lock the sliding device to the flexible belt.

3. A fall-arrest system according to claim 2, wherein the second part is constrained to move relative to the first part from the first position to the second position in a direction parallel to the flexible belt engaging the first part.

4. A fall-arrest system according to claim 2, wherein the first part defines an open channel having a profile configured to receive and retain the flexible belt therein when sliding therealong, the profile being configured to allow the sliding device to pass a linkage anchoring the flexible belt to the ladder.

5. A fall-arrest system according to claim 2, wherein the locking mechanism comprises a locking lever pivotally coupled to the first part, the locking lever having: a distal end furthest from the flexible belt which is pivotally coupled to the second part; and a proximal end closest to the flexible belt which is configured to pivot towards the flexible belt in response to movement of the second part relative to the first part from the first position to the second position.

6. A fall-arrest system according to claim 5, wherein the locking lever is configured to trap the flexible belt between the proximal end and the first part in response to movement of the second part relative to the first part from the first position to the second position.

7. A fall-arrest system according to claim 2, wherein the second part is urged to remain in the second position relative to the first part by a resilient bias.

8. A fall-arrest system according to claim 7, wherein the resilient bias is configured to be exceeded by an opposing force transmitted to the second part by the safety line and created during controlled ascent or descent, whereby the second part moves to the first position.

9. A fall-arrest system according to claim 8, wherein the resilient bias is configured to move the second part from the first position to the second position as soon as the opposing force is removed, and particularly in the event of a person falling from the ladder.

10. A fall-arrest system according to claim 1, wherein at least a portion of the safety line is rigid or substantially rigid such that, when the portion of the elongate track on which the sliding device is positioned is orientated in a vertical or inclined direction, the sliding device is supported on the harness attachment point via the substantially rigid portion of the safety line, maintaining the sliding device above the harness attachment point minimising the distance through which a person might free fall before the locking mechanism is actuated in the event of a fall.

11. A fall-arrest system according to claim 10, wherein the rigid or substantially rigid portion of the safety line comprises a rigid or substantially rigid tube encasing the safety line and wherein the rigid or substantially rigid tube encasing the safety line is slidable therealong.

12. (canceled)

13. A fall-arrest system according to claim 11, wherein the safety line encased by the rigid or substantially rigid tube is wound on a spring-loaded reel within the body of the sliding device such that it is automatically extendible and retractable.

14. A fall-arrest system according to claim 13, wherein the spring-loaded reel comprises a locking mechanism to lock the reel if the reel rotates at a velocity exceeding a predetermined limit which is indicative of a person falling off the ladder.

15. A fall-arrest system according to claim 1, wherein the flexible belt comprises: a first flexible belt component configured to be secured to the ladder; and a second flexible belt component secured to the first belt component by a plurality of linkages spaced along the first and second flexible elongate components, the plurality of linkages being configured to maintain a gap between the first and second flexible belt components and to allow the sliding device to slide freely along the second flexible belt component.

16. A fall-arrest system according to claim 15, wherein the sliding device comprises a part defining an open channel for slidably receiving the second elongate flexible belt component therethrough, the open channel having a profile which is configured to retain the second flexible belt component therein whilst allowing the sliding device to pass at least one of the plurality of linkages when sliding along the second elongate flexible belt component.

17. A fall-arrest system according to claim 15, further comprising at least one coupling configured to secure the first flexible belt component to a rung of the ladder, the at least one coupling being slidable along the first flexible belt between an adjacent pair of the plurality of linkages.

18. A fall-arrest system according to claim 17, wherein the at least one coupling comprises a sleeve through which the first elongate flexible belt component is threaded.

19. A fall-arrest system according to claim 1, wherein the flexible belt has teeth configured to mesh with and rotate a cogwheel rotatably mounted in the sliding device as the sliding device slides along the flexible belt, with the locking mechanism of the sliding device being configured to stop further rotation of the cogwheel if rotation of the cogwheel exceeds a predetermined angular velocity.

20. A fall-arrest system according to claim 1, wherein the flexible belt is configured to be held taut between the upper end of the ladder and a lower end of the ladder.

21. A fall-arrest system according to claim 20, wherein the flexible belt is a continuous loop belt

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

[0058] FIG. 1 is a perspective view of a portable extension ladder being used in a typical application;

[0059] FIG. 2 is a perspective view of a fixed vertical ladder being used in a typical application;

[0060] FIG. 3 is a perspective view of a worker climbing a portable extension ladder in a typical elevated situation whilst using the FAS according to one embodiment of the present invention;

[0061] FIG. 4 is an external perspective view of a sliding device of the FAS in FIG. 3;

[0062] FIGS. 5a and 5b are sectional views of the sliding device of FIG. 4;

[0063] FIGS. 6a and 6b are side and perspective views of a worker climbing a fixed vertical ladder in a typical elevated situation whilst using the FAS in FIG. 3;

[0064] FIG. 7 is a perspective view of a worker exiting the top of a ladder whilst using the FAS in FIG. 3;

[0065] FIG. 8 is a perspective view of a belt track with twin belt components, used in the FAS of FIG. 3;

[0066] FIG. 9 is a perspective view of a worker climbing inside a caged ladder in a typical elevated situation whilst using the FAS according to one embodiment of the present invention;

[0067] FIGS. 10a and 10b show plan and part sectional/part side views of a device for applying tension to a flexible belt; and

[0068] FIG. 11 shows a partly sectioned side view of an embodiment of a belt track incorporating a continuous toothed belt being operated over two pulleys, according to another embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0069] FIGS. 1 and 2 illustrate the two main kinds of the ladder. FIG. 1 is a perspective view of a portable extension ladder being used in the typical application of gaining access to a higher elevation by leaning it against the structure, consisting of overlapping par-axial extensions 1, side members or stiles 2 and rungs 3. FIG. 2 is a perspective view of a vertical ladder being used in the typical application of gaining access to a higher elevation by having previously been fixed to the structure with brackets 4, showing stiles 5 and rungs 6.

[0070] The FAS illustrated and attached to a secured portable ladder 7 in FIG. 3 shows the belt track 8 according to one embodiment of the present invention. (The ladder securing means is not shown, for clarity). This track runs alongside a person's climbing route and is held closely spaced from the ladder by couplings or brackets 9 which are attached to the ladder rungs.

[0071] The person is wearing a safety harness 10, which is connected at a sternal harness attachment point 11 to a rigid safety line 12 of a sliding device 13. The rigid safety line 12 is of fixed length whilst the FAS is operated in the climbing direction, which causes the sliding device 13 to be pushed up the track 8 ensuring that the harness attachment point always remains below the sliding device 13.

[0072] FIG. 4 illustrates one embodiment of the sliding device 13 showing a second part (hereinafter referred to as “the slidable locking frame 14”), constrained within a first part (hereinafter referred to as “the housing 15”), with attachment 16 for safety line 12 and an external lug 17.

[0073] FIGS. 5a and 5b shows the internals of one embodiment of the sliding device 13 as it slides on the belt track 8. FIG. 5a shows the unlocked state of the sliding device, whereupon it is free to slide on the belt track 8. Locking frame 14 is slidably constrained in a direction parallel to the belt track 8 provided by lower slot 18 and upper slot 19 coincidental with lower spindle 20 and upper spindle 21. The locking frame 14 includes the external lug 17 which is pivotally connected by a bolt 23 to the distal end of a locking lever 22, which in addition proximally pivots about spindle 21. Any upwards rotation of the locking lever 22 is resisted by an extension spring 24 which itself is connected to both the locking lever 22 and the housing 15.

[0074] The distal end of the locking lever 22, furthest from the belt track 8, is external to and protrudes through a slot in the housing 15. The proximal surface 25 of the locking lever 22 nearest the belt track, may be serrated, lined with braking material or other roughening means.

[0075] When an upwards pushing force is applied via the safety line 12 when in the climb, or when the weight of the sliding device is applied to the safety line 12 when in the descent, the force, whether the pushing force in the climb or the sliding device weight in the descent, is applied to the safety line attachment, causing the locking frame 14 to slide upwards over spindles 20 and 21, causing the locking lever 22 to pivot upwards about spindle 21, extending extension spring 24 and causing a clearance to be generated between belt track 8 and proximal surface 25 of locking lever 22. As the said pushing force or sliding device weight is indirectly applied to the locking lever 22 via the locking frame 14, any twisting tendency for the sliding device to dig into the into the belt track 8 and impede sliding device movement along the belt track 8, which would occur if the said pushing force or sliding device weight via the safety line 12 were directly applied to the locking lever 22 at connection 23, is otherwise avoided.

[0076] FIG. 5b shows the locked state of the sliding device, which occurs when the locking lever 22 jams against belt track 8 in the event of a fall. When a person initially falls from the ladder, the pushing force if climbing or reaction force to the sliding device weight if descending in the safety line 12 momentarily decays to such an extent that the extension spring 24 pulls the distal end of the locking lever 22 downwards about spindle 21, causing the proximal surface 25 of the locking lever 22 to jam against the belt track 8, such that the sliding device 13 resists any further movement down the belt track 8. This in effect creates an anchor point and so resisting the initial motion of the fall, the continuing momentum of which applies an arrest force downwards via the safety line attachment 16, forcing the locking frame 14 to slide downwards and ipso facto the external lug 17, causing the distal end of the locking lever 22 to be forced downwards about spindle 21 and consequently applying more pressure to proximal surface 25 of the locking lever 22, to such an extent braking contact between proximal surface 25 and belt track 8 defrays the energy of the fall by the friction caused and heat so lost until the fall is brought to a complete stop.

[0077] FIGS. 6a and 6b show the use of one embodiment of the FAS. The person is wearing a safety harness 10, which is connected at a sternal harness attachment point 11 to the safety line 12 of the sliding device 13, which is being pushed up belt track 8 by the climbing action of the person. In this embodiment, the safety line 12 is a composite assembly, comprising an outer rigid tube 26, an inner flexible safety line 27 and a self-retracting reel 28 which connects to the locking frame 14 of the sliding device 13, for storing the inner flexible safety line 27.

[0078] The inner flexible safety line 27 can typically be made of a textile webbing, the lower end of which is connected at the sternal harness attachment point 11 on the safety harness 10. The other end of the inner flexible safety line 27 is attached to and wound on to the self-retracting reel 28. The outer rigid tube 26 is of fixed length, encases and is able to slide on the inner flexible safety line 27 but is not attached to it, nor is it attached to self-retracting reel 28 or harness attachment point 27.

[0079] The self-retracting reel 28 comprises the wound storage of a length of inner flexible safety line 27, a torsion spring and an inertial locking mechanism (all not shown). The purpose of the torsion spring is to maintain a light tension on the inner flexible safety line 27 at all times and facilitates the automatic extraction and retraction of the safety line 27 in response to the person's movement, without any slack being able to develop in the safety line 27, much like the passenger retracting seat belt arrangement found in modern motor vehicles.

[0080] When a person climbs up a ladder, the harness attachment point 11 abuts the bottom of the outer rigid tube 26 and said tube being rigid, pushes against the reel 28 and sliding device 13, causing the sliding device 13 to slide up the belt track 8. When descending, the weight of the sliding device 13 and reel 28 cause the sliding device to slide down the belt track 8. Both in the climb and descent the length of inner flexible safety line 27 extracted from reel 28 and inside the outer rigid tube 26 remains the same length as the outer rigid tube 26.

[0081] In the event of a fall, the sliding device 13 locks to the belt track 8 as described above. This causes the inner flexible safety line 27 to rapidly extract from the self-retracting reel 28. When this extraction speed reaches a pre-determined limit, the inertial locking mechanism inside the reel causes the reel to lock about its spindle and to prevent further extraction. This decelerates and brings to the fall to a halt. The outer rigid tube 26 slides down the inner flexible safety line 27 in response to the extraction and exposes the said safety line where it exits the reel 28.

[0082] This particular arrangement has no real advantage over the basic, fixed length safety line embodiment shown in FIG. 3, until the situation is considered where a person wishes to exit from the top of the ladder, as shown in FIG. 7.

[0083] It is essential to facilitate protection from falling when transiting from the ladder onto an adjacent surface or platform, as often this movement can be difficult from an ergonomic viewpoint, for instance when stepping over a guard rail or scaffold pole as shown in FIG. 7, and exposes persons so doing to a risk of falling. Sometimes this movement can be so difficult that a person will disconnect themselves from the very FAS that is protecting them, in order to facilitate the transfer, which can be very dangerous.

[0084] FIG. 7 shows a person exiting from the top of a secured ladder, (method of securing not shown), whilst negotiating a guard rail in order to gain access to the level on the safe side of the guard rail, utilising the same embodiment of the invention as described in FIGS. 6a and 6b, said person wearing a safety harness 10, which is connected at the sternal harness attachment point 11 to the composite safety line 12 of the sliding device 13, which is on belt track 8.

[0085] The advantage of the composite safety line assembly 12, is that during the climb, the composite safety line assembly 12 is of fixed length, necessary to ensure that the sliding device 13 is maintained at a position above the harness attachment point 11 in order to minimise free fall, whereas when coming to exit from the ladder, the composite safety line assembly 12 becomes variable in length, facilitated by the self-retracting reel 28. The extraction and retraction of the safety line 12 in response to the person's movement, whilst preventing slack developing in the safety line, allows, in particular, those movements and postures requiring a greater length of safety line than that in the climb, to be adopted in order to negotiate exiting from the ladder, without having to disconnect from the FAS and therefore providing full protection from falling.

[0086] FIG. 8 shows an embodiment of the belt track invention, which consists of twin or first and second belts, the rearmost belt 30 and the frontmost belt 29. The two belts are joined at intervals using a plurality of linkages or spacers 31. The uppermost and lowermost portions of the twin belts where they connect to the ladder are not shown.

[0087] The rearmost belt 30 is installed nearest the ladder and is threaded through belt receiving sleeves 32 that completely encircle the belt 30. The belt receiving sleeves 32 form part of the couplings or brackets 9 that are secured to the ladder rungs (FIG. 3) at intermediate positions between the upper and lower attachment points of the belts to the ladder.

[0088] During installation, the belt receiving sleeves 32 may be moved along the rearmost belt 30 in between spacers 31, allowing alignment with a rung for attachment purposes despite any variations of rung pitch.

[0089] The frontmost belt 29 is installed so to be nearest the person climbing the ladder and provides the portion of the track upon which the sliding device 13 slides in response to normal climbing or descending movement and locks to the frontmost belt 29 in the event of fall (FIG. 5).

[0090] The belt spacers 31 and the sliding device 13 are formed so that displacement of the sliding device 13 along the track is not obstructed by the spacers 31 or the belt receiving sleeves 32. For example, the sliding device 13 comprises a part defining an open channel for slidably receiving the frontmost belt 29 therethrough, the open channel having a profile which is configured to retain the frontmost belt 29 therein whilst allowing the sliding device 13 to pass at least one of the plurality of linkages 31 when sliding along the frontmost belt 29.

[0091] The use of the FAS according to one embodiment of the present invention is shown in FIG. 9 in the situation where a person has to climb inside a caged ladder 33, comprising belt track 8, safety harness 10, rigid safety line 12 and sliding device 13. The rigid safety line 12 is of fixed length whilst the FAS is operated in the climbing direction, which causes the sliding device 13 to be pushed up the track 8 ensuring that the harness attachment point always remains below the sliding device 13. This ensures that in a fall scenario free fall is minimised and fall motion tends to be inwards away from the cage, both of which minimise the potential for secondary injuries caused by localised impacts which may occur when in the confines of a cage.

[0092] FIGS. 10a and 10b show plan and part sectional/part side views of a device for applying tension to a flexible belt track 8. The device includes a belt securing clip 34 for releasably engaging the flexible belt track 8, and an arrangement with an over-centre tensioning latch 35 which in use is configured to be secured to the ladder 7. The belt securing clip 34 is threaded onto the flexible belt track 8. A lever of the over-centre tensioning latch 35 is raised to its highest position until a spring 36 is hooked onto the belt securing clip 34. Excess slack in the flexible belt track 8 is taken up before a clamping cam lever 37 of the belt securing clip 34 is moved to clamp the flexible belt track 8 and a retaining pin 38 is inserted behind the flexible belt track 8. The lever of the over-centre tensioning latch 35 is moved downwards to apply tension to the flexible belt track 8 via the spring 36. A tension retaining pin 39 may then be used to anchor the belt securing clip 34 to the ladder 7.

[0093] FIG. 11 shows an embodiment of further aspect of the present invention, which consists of a continuous toothed belt 54 which is looped and tensioned around the front and rear of a ladder and an upper pulley 56 and lower pulley 57. For clarity, the brackets 4 that fix the ladder to structure are not shown. A clamp 55 is clamped to the toothed belt 54. The rigid safety line 12, is connected between the safety harness 10 worn by the person climbing the ladder and the clamp 55.

[0094] As the clamp 55 is fixed to the toothed belt 54, any climbing or descending movement of the person is transmitted via the rigid safety line 12, causing the toothed belt 54 to be moved upwards or downwards. The upper pulley 56 and lower pulley 57 have radial teeth spaced with grooves (not shown) that mate with the teeth of the toothed belt 54, such that up and down movement of the toothed belt 54 causes the both pulleys to rotate.

[0095] The upper pulley 56 contains an internal locking mechanism (not shown) which is sensitive to angular velocity, similar in operation to the reel described in FIG. 6a. When the toothed belt 54 is pushed up and down by climbing or descending movement, the upper pulley is spun in response by it being mated with the toothed belt 54 but at an angular velocity insufficient to actuate the locking mechanism of the upper pulley 56. If a fall occurs, the sudden gravitational plummet causes the toothed belt to pulled downwards rapidly, causing the locking mechanism of the upper pulley 56 to operate due to the sudden increase in angular velocity, similar in function to the retractable seat belt of a modern motor vehicle, causing the fall to be arrested.

[0096] The lower pulley 57, having no internal locking mechanism, simply spins in response to normal climbing movement or the rapid movement associated with a fall. After a fall has taken place and the arrested person is left in suspension on the toothed belt 54, a cranking handle 58 may be inserted within the lower pulley 57 for the purposes of remotely rescuing the faller by a second person on the ground or other safe platform.

[0097] The cranking handle 58 may be turned initially to raise the arrested person, releasing the locking mechanism of upper pulley 56, so that it becomes free again to spin on its axis and allowing the second person to slowly lower the arrested person to the ground or other safe platform. This arrangement is advantageous in that an arrested person can be remotely rescued by a second person from a place of safety without the need to climb the ladder and put themselves at risk of another fall, it eliminates the need for any additional rescue equipment or services and the rescue can be effected in a rapid timescale in order to minimise the possibility of the arrested person becoming endangered by the debilitating effects of any injury or suspension trauma, the latter of which has the capability of causing expiration through a collapse in metabolism caused by motionless suspension in a safety harness.

[0098] Various additional features may be used with or incorporated with the present invention without departing from its scope, which are not illustrated, as follows:

Any of the embodiments of the invention may be applied to a vertical or leaning ladder.
Rest platforms may be installed at intervals up the ladder.
Gate devices may be installed at any point on the track, irrespective of orientation, to allow the sliding device to be attached or detached at those points according to work requirements. Alternatively, an opening device may be incorporated within the sliding device itself, to allow it to be attached to or detached from the track at any point.
Turntables or switches, which enable a person to transfer the sliding device from plane to plane, or to transfer between near-parallel routes.
Leaning ladders may be lashed to the supporting structure.
Leaning ladders may be stabilised with an effective ladder stability augmentation device.