AU2018101477A4 - Inline descender - Google Patents

Abstract

Abstract An inline descender for belaying a load tethered to a rope, which has a body defining a series of apertures. The body has an anchor end configured to attach to a fixed point and a load end which faces the rope extending to the load. The series of apertures extending in a line towards the load end, define a serpentine path for the rope to thread back and forth through from one side of the body to an opposite side. The aperture nearest the load end is wider in the direction of the rope extending to the load than at least one of the other apertures. This decreases the curvature of the rope bend between the last apertures at the load end, which in turn decreases the forces in the transverse direction on the body at the load end. With more uniform transverse loads on the body along its length, the load end is less prone to plastic deformation and the load capacity is increased.

Description

Inline Descender

Field of the Invention [0001] The present invention relates to devices used to belay the descent or movement of a load secured to a rope. In particular, the invention relates to a device known as an inline descender used to belay a rope holding a load such as a suspended weight.

Background of the Invention [0002] Activities such as rock-climbing and abseiling will typically tether the climber to an overhead anchor via a rope. Often the rope feeds through the anchor and back to the climber or another person via a belay device. The rope generates friction as it is drawn through the belay device to slow feed rate, which in turn reduces the rate of descent for the climber.

[0003] Many other occupations use belaying devices to slow the descent of a suspended load, such as firefighters, helicopter rescue personnel, tree loppers, acrobats, movie stunt performers and so on.

[0004] One type of belay is known as an inline descender which has a series of apertures extending in a line through a rigid body. Typically the rigid body is a unitary metal component. One end of the inline descender is anchored (to the ground or other fixed point) and the rope is threaded back and forth through the descender via the apertures. The load creates enough tension to draw the rope through the apertures. Friction against the side of the apertures resists this weaving movement of the rope and reduces the tension at the tail end of the rope so a person can manually feed the rope at a controlled rate.

[0005] Inline descenders have a maximum load capacity at which the structures and components will not fail or plastically deform. However, at times the suspended load may drop or freefall before it is suddenly arrested by the rope tether. This can shock load the device and inadvertently generate loads exceeding the maximum threshold resulting in plastic deformation or fracture of some components.

[0006] Throughout the specification, the use of the term ‘rope’ is understood to include loads tethered or suspended via a cable, tendon, cord, line, strap or any other type of flexible tether for a load.

[0007] Any reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

[0008] Throughout the description and claims of the specification, the word “comprise” and variations of the word, such as “comprising” and “comprises”, is not intended to exclude other additives, components, integers or steps.

Summary of the Invention [0009] In light of the above, the present invention provides an inline descender for belaying a load tethered to a rope, the descender comprising: a body defining a series of apertures, the body having an anchor end configured to attach to a fixed point and a load end which faces the rope extending to the load when in use, the series of apertures extending in a line towards the load end to define a serpentine path for the rope to thread back and forth through from one side of the body to an opposite side; wherein, the aperture nearest the load end is wider in the direction of the rope extending to the load than at least one of the other apertures.

[0010] The Applicant’s ongoing development of these devices has found that overload failure will often first appear as plastic deformation of material between the aperture closest the load end, and its adjacent aperture (i.e. the second closest aperture). The metal or other material between these apertures is pushed ‘sideways’ (i.e. transverse to the length of the descender body) by the bend of rope trying to straighten as the tension from the load increases past the maximum threshold. The tension in the rope bend closest the load end is greater than that of the other rope bends, as the friction against the sides of the apertures progressively reduces the rope tension with every additional rope bend away from the load end. This is the basic mechanism allowing a single person to belay heavy loads. However, with the highest tension at the load end, it is this portion where the yield strength of the body will be exceeded. Widening the aperture of the load end increases the curvature of the rope around the section between the two apertures closest the load end and this reduces the transverse component of the force on this section of the body.

[0011] The tension in the rope bend between two of the apertures can be notionally resolved into a component parallel to the length of the descender and a component transverse to the length dimension. This is described in greater detail below and illustrated in Figure 2. With a wider curvature, the transverse component is reduced so that the loads are more evenly distributed throughout the descender. In this way, the area between the final two apertures at the load end is less prone to failure or plastic deformation prior to other sections of the descender. In turn, this effectively increases the load capacity of the descender.

[0012] Preferably, the aperture second closest the load end is also wider in the rope direction than at least one of the other apertures.

[0013] Preferably, the load end of the body is not configured for anchoring to a fixed point in order to avoid use of the descender in an orientation opposite to the intended orientation.

[0014] Preferably, the apertures have rounded peripheries to smooth a transition from a side surface of the body to an internal surface of the aperture, the rounded periphery of the aperture closest the load end having a greater radius than that of at least one of the other apertures.

[0015] Preferably, at least some of the apertures are provided as a slot extending into the body from a side edge, such that an intermediate section of the rope can be inserted into the slot rather than an end of the rope being threaded through the apertures, and the descender further comprising a moveable gate to selectively open and close an opening to the slot in the side edge, the gate being attached to the body with a threaded fastener and the body having an internally threaded bore extending into the side edge, the depth of the bore being less than a third of the body width from the side edge to the opposing side edge.

Brief Description of the Drawings [0016] Preferred embodiments of the present invention will now be described for the purposes of illustration only, with reference to the accompanying drawings in which: [0017] Figure 1 is a schematic representation of an inline descender according to the present invention used to belay the descent of a load suspended by a rope; [0018] Figure 2 is a schematic section view through the apertures of the inline descender shown in Figure 1.

[0019] Figure 3 is a perspective view of the inline descender according to the present invention; [0020] Figure 4 is an exploded perspective showing the side opposite that of Figure 3; [0021] Figures 5 to 8 are side elevations, end elevation and plan view of the integrally cast aluminium body of the descender; and [0022] Figure 9 is a perspective view of the aluminium body shown in isolation.

Detailed Description of the Preferred Embodiments [0023] Referring to Figure 1, the inline descender 2 is shown belaying the descent of a load 14 suspended from an elevated position 74 by a rope 12. The tension 60 in the rope 12 matches the weight 76 of the load 14. However, the tension 70 in the tail portion 18 of the rope 12 is much less than the rope tension 60 on the load side of the descender 2. Accordingly, the descent of the load 14 is belayed by manually controlling the feed rate into the descender 2.

[0024] The descender 2 has a body 4, of 6061 grade aluminium with an anodised surface finish. The body has an anchor end 8, a load end 6 and a series of apertures 16. The anchor end is configured for secure attachment to a fixed point 10 such as the ground or other mounting site. Typically, the anchor end 8 has an eyelet large enough to receive a carabiner with a suitable strength rating. However, skilled workers in this field will readily appreciate that other attachment configurations are possible, bearing in mind the need to avoid any stress concentrating geometries.

[0025] As shown in Figure 2, the rope 12 is threaded through the apertures 16 in a serpentine path. The friction 42 against the sides of the apertures 16 reduces the tension 70 in the tail 18 of the rope 12, while the combined friction forces 72 are transferred to the anchor 10. Therefore, it will be understood that the rope tension 60 is greater at the load end 6 than the anchor end 8. As discussed above, the structures of the body 4 at the load end 6 are more likely to fail before sections closer to the anchor end 8 because of the higher stresses. To address this, the descender 2 of the present invention provides an aperture 20 nearest the load end 6 that is wider in the rope direction than at least one, if not most of the other apertures 16.

[0026] The structural benefits of widening the aperture 20 are illustrated in the schematic vector diagrams on Figure 2. The body 4 of the descender is shown sectioned through the apertures 20, 24, 28, 32 and 36. Similarly, the rope 12 is shown weaving through the apertures from the anchor end 8 to the load end 6. At the load end 6, the rope tension 60 is greatest and equal to the weight 76 of the load 14 (see Figure 1). Friction 42 between the rope 12 and the periphery of the apertures progressively reduces the rope tension with each rope bend 44, 46, 48, 50 and 52.

[0027] The tension in the rope 12 extending through the aperture 20 is schematically represented by arrow 54. This may be notionally resolved into a transverse component 58 and a longitudinal component 56. The transverse component 58 must be resisted by the body section 26 extending between the apertures 20 and 24. The other body sections 30, 34 and 38 positioned between apertures also provide the structural stiffness to resist the transverse components at rope ends 46, 48 and 50 respectively. However, as discussed above, the total rope tension 64 has been reduced by the friction forces 42 and therefore the notional component forces 66 and 68 are likewise reduced.

[0028] In light of this, if apertures 20, 24, 28, 32 and 36 were identical, the body section 26 would experience the greatest transverse loading 58 and therefore be the first to fail when the yield strength is exceeded. To address this, the width of the aperture 20 is increased in the rope direction, such that the rope is not as tightly curved about the body section 26. This effectively reduces the angle of the rope tension 54 within the aperture 20, thereby reducing the transverse component 58. With a lower transverse component 58, the friction 42 on the section 26 is lower resulting in greater rope tension within the next aperture 24. In turn, this means the rope bend 46 will have a slightly increased transverse force component acting on it relative to the case where all apertures are identical. Therefore, by widening the aperture 20, the transverse loads on each of the sections 26, 30, 34 and 38 are more uniformly distributed. By removing the high stress area at section 26, the overall descender 2 has an increased load capacity.

[0029] The second-last aperture 24 at the load end 6 may also be widened as shown in the example illustrated in Figures 3 to 9. As discussed above, the tension in the rope reduces progressively from the load end to the anchor end. Therefore, the rope tension in the bend through the second last aperture 24 is also higher than that nearer the anchor end, particularly when the last aperture 20 has been widened. Widening the aperture 24, preferably less than aperture 20 is widened, will distribute the transverse loads even more evenly along the descender 2. In fact, each aperture may be progressively widened from the anchor end to the load end, bearing in mind the serpentine rope path will still need to generate sufficient friction to belay the load. This can be used to ensure the transverse loading on each body section between adjacent apertures is the same (equal but opposite to the next rope bend) so that there are no portions that are prone to failure before any other section. This effectively increases the load capacity of the descender.

[0030] Figures 3 and 4 shown one form of the descender 2 without the rope threaded through the series of apertures 16. The body 4 is cast 6061 aluminium with a carabiner eyelet 82 at the anchor end 8 and a significantly smaller hole 78 at the load end 6. Descenders are typically anchored using a carabiner rated to the required strength. The eyelet 82 is sized to easily receive the carabiner but the hole 78 is not large enough to fit the same sized carabiner. This aims to ensure the descender is used in the correct orientation as the functional benefits discussed above would be lost if the rope were drawn through the apertures in the opposite direction. As a further safeguard, a rope direction arrow 80 is pressed into the side of the body 4.

[0031] As best shown in Figure 4, the apertures in the body 4 have radiused peripheries 84 to smooth the transition from the side surfaces into each aperture. The skilled worker in this field will readily understand this provides smoother operation and reduces wear on the rope.

[0032] The peripheral radius 84 does not need to be uniform for each aperture. In the wide aperture 20 closest the load end 6, the peripheral radius 84 may be larger than that of the other apertures 24 to 36. The larger radius periphery 84 around the widest aperture 20 can be used to further reduce the curvature on the rope bend between aperture 20 and aperture 24.

[0033] As best shown in Figures 4 to 9, the apertures 20 to 36 are provided in the form of slots extending into the body 4 form its top edge (as shown in the Figures). Providing the apertures as slots allows the rope to be inserted into the apertures via the openings 100, rather than threading an end of the rope back and forth through each of the apertures.

[0034] To retain the rope in the apertures, especially when not under tension, sliding gates 86 and 88 are provided to cover the aperture openings 100 in the top edge of the body 4. These sliding gates 86 and 88 are retained on the body 4 via externally threaded spigots 90 which engage bores 98, having a complimentary internal thread. The spigots 90 extend through longitudinal slots 96 in each of the sliding gates 86 and 88 respectively. The sliding gates 86 and 88 are securely held in place by tightening internally threaded turnbuckles 92 down the externally threaded spigots 90. The turnbuckles 92 apply compressive force onto the sliding gates 86 and 88 via steel washers 94. Loosening the turnbuckles 92 allows the gates to be longitudinally slid relative to the body 4 to expose selected aperture openings 100. The threaded studs 90 are designed to keep the turnbuckles captive on the threaded studs to avoid them being lost or misplaced. The end of the threaded stud 90 has a machined radius of greater diameter than the thread size in the turnbuckle, to retain each turnbuckle on its stud.

[0035] Skilled workers in this field will understand that the sides of the aperture openings are slowly inclined to the longitudinal axis of the body 4, as a ready indication as to how the rope is to thread back and forth to the apertures 20 to 36.

[0036] The internally threaded bores 98 are shown in the Figures as 5mm diameter bores extending 17mm into the body sections 26 and 38 respectively. The applicants development of this descender has shown that keeping the depth of the bores 98, the 63.5mm height of the body 4 (in this case a 17mm bore depth is less than one third the 63.5mm body height), maintains greater structural strength and integrity of the body 4.

[0037] The invention has been described herein by way of example only. Skilled workers in this field will readily recognise many variations and modifications which do not depart from the spirit and scope of the broad inventive concept.

Claims (5)

The claims defining the invention are as follows

1. An inline descender for belaying a load tethered to a rope, the descender comprising: a body defining a series of apertures, the body having an anchor end configured to attach to a fixed point and a load end which faces the rope extending to the load when in use, the series of apertures extending in a line towards the load end to define a serpentine path for the rope to thread back and forth through from one side of the body to an opposite side; wherein, the aperture nearest the load end is wider in the direction of the rope extending to the load than at least one of the other apertures.

2. An inline descender according to claim 1, wherein the aperture second closest the load end is also wider in the rope direction than at least one of the other apertures.

3. An inline descender according to claim 2, wherein the load end of the body is not configured for anchoring to a fixed point in order to avoid use of the descender in an orientation opposite to the intended orientation.

4. An inline descender according to claim 3, wherein the apertures have rounded peripheries to smooth a transition from a side surface of the body to an internal surface of the aperture, the rounded periphery of the aperture closest the load end having a greater radius than that of at least one of the other apertures.

5. An inline descender according to claim 4, wherein at least some of the apertures are provided as a slot extending into the body from a side edge, such that an intermediate section of the rope can be inserted into the slot rather than an end of the rope being threaded through the apertures, and the descender further comprising a moveable gate to selectively open and close an opening to the slot in the side edge, the gate being attached to the body with a threaded fastener and the body having an internally threaded bore extending into the side edge, the depth of the bore being less than a third of the body width from the side edge to the opposing side edge.