GB2437074A

GB2437074A - Safety line for absorbing shock

Info

Publication number: GB2437074A
Application number: GB0607247A
Authority: GB
Inventors: David Millership
Original assignee: MAXESS Ltd
Current assignee: MAXESS Ltd
Priority date: 2006-04-11
Filing date: 2006-04-11
Publication date: 2007-10-17
Anticipated expiration: 2026-04-11
Also published as: GB2437074B; WO2007116202A1; GB0607247D0

Abstract

A horizontal safety line 16, to which a worker 54 is attached by a lanyard 52, extends between a reel 10 and an anchor point 46. Reel 10 includes a lock to fix the length of the line spooled from it and the reel is connected to a second anchor point 48 through a shock-absorbing means 24 which extends when subject to a tensile force greater than a predetermined amount. The shock-absorbing means and/or the safety line may comprise liquid crystal polymer fibre.

Description

Safety Line Apparatus The present invention relates generally to safety

line apparatus and more specifically to horizontal personal safety line apparatus.

Safety regulations increasingly demand that safety lines be provided for workers at high levels, eg, on roofs or steel frameworks of buildings. A horizontal safety line may be used at exposed sites as a handrail and for attachment of a sliding karabiner on a lanyard of a British Patent Application GB2269623 describes a horizontal safety line which is facilitated by two sections of webbing, the distal ends of which are fixed to anchor points on, for example, scaffolding and proximal ends are linked by way of a rachet that allows the line' to be tensioned. A worker may attach himself to this line by way of a lanyard, which may be a section of webbing having an integral shock absorber, the webbing being attached at a proximal end to a harness worn by the worker and having a karabiner, at a distal end, for enabling the lanyard to be slidably attached to the horizontal line.

If the worker should fall, the integral shock absorber generally causes the overall length of the lanyard to increase (due to the tensile force applied to it), thereby providing damping which helps to prevent shock-related injury to the worker.

However, this type of safety line apparatus has a significant drawback in that the shock absorber causes the lanyard to extend in length when a worker falls to the extent that if the worker is operating at a height less than the resultant length of the lanyard, he will hit the ground before his fall is arrested.

It is therefore an object of the present invention to provide a horizontal safety line that is effective in arresting the fall of a worker operating at lower heights, relative to prior art systems.

In accordance with the present invention there is provided safety line apparatus for providing a tensioned safety line between first and second anchor points, the apparatus comprising spooling means housing said safety line, said safety line having a free end by means of which it can be extended from said spooling means and anchored at said first anchor point, the apparatus further comprising shock absorbing means, one end of which is connected to said spooling means and the other end of which can be anchored at said second anchor point.

Thus, the above mentioned object is achieved by providing a shock absorber in-line with the safety line on the opposite side of the spool to the free end of the safety line. Further, this arrangement enables the provision of a compact, one-piece horizontal safety line that may be less than 1kg in weight and less cumbersome relative to prior art arrangements.

Preferably, said spooling means is operable in respective first and second configurations and comprises controlling means for selectively setting the mode of operation to either said first or said second configuration. Beneficially, when in said first configuration, said safety line can be freely extended from and returned to said spooling means. In said second configuration, said spooling means is preferably configured to operate as a ratchet by way of a rachet means, such that the length of said safety line extending from said spooling means may not be extended any further but may be shortened.

Beneficially, said safety line apparatus further comprising locking means for locking said safety line at a desired length extended from said spooling means such that it cannot be further extended from, or retracted into said spooling means and a single controlling means is preferably used to select the mode of operation of said spooling means and to operate said locking means.

Preferably, said spooling means incorporates a metal tension frame and said tension frame beneficially comprises a first and second portion, having intersecting cross-members that may act as anchor points for components attached to said spooling device. Preferably, said tension frame comprises stainless steel and said tension frame beneficially has a honeycomb structure.

Beneficially, said shock absorbing means extends in length when subject to a tensile force exceeding a predetermined threshold and said shock absorbing means preferably comprises a portion of line that is gathered and bound by binding means.

Preferably, said free end of safety line terminates in a universal end fixing and said free end of said shock absorbing means beneficially terminates in a universal end fixing.

Beneficially, said line forming said shock absorbing means andlor said safety line comprise liquid crystal polymer fibre.

These and other aspects of the present invention will be apparent from, and elucidated with reference to, the embodiment described herein.

An embodiment of the present invention will now de described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional diagram of a spooling device according to an exemplary embodiment of the present invention showing the safety line; Figure 2 is a schematic cross-sectional diagram of the spooling device of Figure 1, showing the ratchet mechanism (in its "ratchet" position); Figure 3 is a schematic cross-sectional diagram of the spooling device of Figure 1, showing the ratchet mechanism (in its "closed" position); Figure 4 is a schematic cross-sectional diagram of the spooling device of Figure 1, showing the ratchet mechanism (in its "open" position); Figure 5 is a schematic cross-sectional diagram of the spooling device of Figure 1, showing the tension frame; Figure 6 is a schematic diagram of a workman attached to a horizontal safety line according to an exemplary embodiment of the present invention, pre-fall; and Figure 7 is a schematic diagram of the workman of Figure 6, post-fall.

Referring to Figure 1 of the accompanying drawings, a spooling device 10 according to an exemplary embodiment of the present invention is shown, comprising a generally circular, hollow, casing 12 having an aperture on its circumferential face. Fixed within the aperture is a guide member 18, having smooth geometry that facilitates a substantially frictionless passage though the aperture. The guide member 18 may comprise any material that is durable and will not be worn easily by frequent abrasion due deployment and retraction of the safety line 16. The material should also be smooth to ensure minimal friction between the guide member 18 and the safety line 16. A central spindle 14 is mounted at a substantially central position within the casing 12, attached to which is a safety line 16 that Jo may coil around the central spindle 14 as the spindle 14 rotates. The central spindle 14 may comprise a portion of stainless steel bar, however any material with suitable strength characteristics may be used. The safety line 16 passes through the guide member 18 and, at a distal end to that which is attached to the central spindle 14, the safety line 16 tenninates in a universal end fixing (not shown) that may be easily attached to a range of generally mutually exclusive but variable anchor points. The universal end fixing may be a 25mm closed soft eyelet and karabiner that can accommodate a range of end fixings for attachment to steelwork, scaffolding, fixed anchors or the like. The safety line 16 may comprise liquid crystal polymer fibre, however, any material with exceptional strength and fatigue-resistance and low stretch or creep characteristics may be used. The safety line 16 may have a variable span ranging from 2m minimum, to 8m maximum, and may be fully retractable within the spooling device 10. The safety line 16 may have one or more coloured strands integrated therein that may act as wear indicators. When a colour or certain colours become visible it indicates that the line 16 has worn sufficiently to require replacement.

On a generally opposite side of the circumferential face of the casing 12 (relative to the guide member 18) is a further aperture that allows one end of a shock absorbing means 24 to pass into the casing 12. This proximal end of the of the shock absorbing means 24 is fixed to an internal anchor member 22. The distal end of the shock absorbing means 24 terminates in a universal end fixing 26 that may be easily attached to a range of generally mutually exclusive but variable anchor points. The shock absorbing means 24 may comprise a length of polyamide, polypropylene, or polyester integral tear webbing, gathered and stitched in such a way that it will not tear when the safety apparatus is tensioned and used, but will tear when subject to a tensile force applied due to the weight of a falling workman. In this exemplary embodiment of the present invention, the apparatus has a maximum deflection under load of 800mm with the shock absorber means 24 activated. It will be apparent to a person skilled in the art that many other forms of shock absorbing means could be used to provide damping, for example an elastic member, such as a spring.

A layering or tensioning member 20 is provided within the casing 12, that is in substantially constant contact with one face of the safety line 16 when coiling andlor uncoiling and thus aids uniform winding around the central spindle and helps to prevent the safety line 16 from becoming tangled (this problem is known in the art as bird nesting').

Referring now to Figures 2, 3 and 4 of the accompanying drawings, a rachet mechanism (located within a spooling device 10 according to an exemplary embodiment of the present invention) is shown, comprising a sloping-toothed wheel 36 mounted concentrically with, and fixed to, the central spindle 14. A double pawl 30 is rotatably mounted in spaced apart relation thereto on an axle 38, such that an end of the pawl 30 may engage a sloping-toothed part of the sloping-toothed wheel 36 and restrict rotation of the sloping-toothed wheel 36 (and thus the central spindle 14) in one direction. A spring means 34 is provided to force the paw! 30 towards the sloping-toothed wheel 36. A distal end of the pawl 30, to that which may engage the sloping-toothed wheel 36, is shaped and configured to provide a trigger portion 40 that may be used by a workman to apply force in a direction that forces the pawl 30 away from the sloping-toothed wheel 36. Locking means 32 are rotatably provided in proximity to the pawl axle 38 such that the pawl 30 may be either locked in a open position (as can be seen in Figure 4), allowing the sloping-toothed wheel 36 to freely rotate in either direction, locked in a closed position (as can be seen in Figure 3), preventing movement in either direction or it may be unlocked (as can be seen in Figure 2), thereby allowing a ratchet actuation, i.e. in only one direction.

The central spindle 14 protrudes from the casing 12 and at this point is configured as a hexagonal nut that can be turned using, for example, a 7/16 swing spanner offering suitable torque. It is by way of this that a workman can wind in or wind out the safety line 16 from the spooling device 10.

Referring now to Figure 5 of the accompanying drawings, a tension frame 42 is shown located within the casing 12 of a spooling device 10 according to an exemplary embodiment of the present invention. The tension frame 42 may comprise two symmetrical portions as shown, configured such that one is adjacent to either inside-face of the casings 12,the spool 14, anchor 22, axle 38, tensioning member 20 and the like are mounted therebetween. The tension frame 42 may comprise stainless steel and may have a honeycomb structure for reducing its mass. It will be appreciated that this configuration provides an arrangement having excellent tensile properties between the safety line 16 and shock absorbing means 24, whilst remaining substantially light and compact.

Referring now to Figure 6 of the accompanying drawings, a workman 44 is shown standing on a section of scaffolding 50. A safety line is connected at one end to a first anchor point 46. The workman 44 is connected to the safety line 16 by way of a lanyard 52 that may have a karabiner fixed to a distal end to allow the lanyard 52 to be movably attached to the safety line 16. The lanyard 52 has no integral shock absorbing means and may be approximately im in length. The proximal end may be fixed to a harness 54 worn by the workman 44. The spooling device 10 can be seen towards the left hand side of the Figure, adjacent to the shock absorbing means 24, which in turn is removably fixed to a second anchor point 48. By way of this arrangement the workman may fully traverse the scaffolding 50 in a horizontal direction.

Referring now to Figure 7, a situation is depicted whereby the workman 44 has fallen from the scaffolding. The shock absorbing means 24 has extended due to the tensile force exerted upon it as the workman falls, and the degree of extension (and therefore degree of shock absorption) is comparable to that of the prior art system, however, because of the positioning of the absorbing means 24, the overall distance the workman 44 falls is reduced (as most of the overall extension is in the horizontal component, rather than being mostly vertical), meaning that the apparatus is capable of arresting him within a fall-height' of less than 4m.

It should be noted that the above-mentioned embodiment illustrates rather than limits the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The word "comprising" and "comprises", and the like, does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. The invention may be implemented by means of hardware comprising several distinct elements. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS: 1. Safety line apparatus for providing a tensioned safety line

between first and second anchor points, the apparatus comprising spooling means housing said safety line, said safety line having a free end by means of which it can be extended from said spooling means and anchored at said first anchor point, the apparatus further comprising shock absorbing means, one end of which is connected to said spooling means and the other end of which can be anchored at said second anchor point.

2. Safety line apparatus according to claim 1, wherein said spooling means is operable in respective first and second configurations and comprises controlling means for selectively setting the mode of operation to either said first or said second configuration.

3. Safety line apparatus according to claim 2, wherein in said first configuration, said safety line can be freely extended from and returned to said spooling means.

4. Safety line apparatus according to either of claims 2 or 3, wherein in said second configuration, said spooling means is configured to operate as a ratchet by way of a rachet means, such that the length of said safety line extending from said spooling means may not be extended any further but may be shortened.

5. Safety line apparatus according to either of claims 3 or 4, further comprising locking means for locking said safety line at a desired length extended from said spooling means such that it cannot be further extended from, or retracted into said spooling means.

6. Safety line apparatus according to claim 5, wherein a single controlling means is used to select the mode of operation of said spooling means and to operate said locking means.

7. Safety line apparatus according to any preceding claim, wherein said spooling means incorporates a metal tension frame.

8. Safety line apparatus according to claim 7, wherein said tension frame comprises a first and second portion, having intersecting cross-members that may act as anchor points for components attached to said spooling device.

9. Safety line apparatus according to either of claims 7 or 8, wherein said tension frame comprises stainless steel.

10. Safety line apparatus according to any of claims 7 to 9, wherein said tension frame has a honeycomb structure.

11. Safety line apparatus according to any preceding claim, wherein said shock absorbing means extends in length when subject to a tensile force exceeding a predetermined threshold.

12. Safety line apparatus according to claim 13, wherein said shock absorbing means comprises a portion of line that is gathered and bound by binding means.

13. Safety line apparatus according to any preceding claim, wherein said free end of safety line terminates in a universal end fixing.

14. Safety line apparatus according to any preceding claim, wherein said free end of said shock absorbing means terminates in a universal end fixing.

15. Safety line apparatus according to claim 12, wherein said line forming said shock absorbing means andlor said safety line comprise liquid crystal polymer fibre.

16. Safety line apparatus substantially as herein described with reference to the accompanying drawings.