Patent application title: Apparatus for Climbing a Rope
Michael James Spraggon (Towersey, GB)
IPC8 Class: AA63B2700FI
Class name: Fire escape, ladder, or scaffold pole or strand grasping-type climber foot- or leg-attachable
Publication date: 2013-05-30
Patent application number: 20130133981
The invention provides an ascender or other rope-gripping device which is
separated form its handle by a connection of length such that when, in
use, the ascender is attached to a single rope suspended from above with
a second, handled ascender below it. The second ascender can be lifted up
along the rope to a position where its associated handle is above the
handle of the first ascender.
37. For inclusion in apparatus for use in climbing a single rope suspended from above, the apparatus comprising a pair of mutually independent, hand operated ascenders of different lengths, each comprising rope gripping means situated in the ascender's upper part, the ascender's lower part being shaped for use as a handle, and a foot stirrup suspended from a lower part of each ascender, a first ascender the rope-gripping means of which is separated from the handle thereof sufficiently that, in use of the apparatus, when the rope-gripping means of the first ascender is positioned on the rope above the rope gripping means of the second ascender, the rope-gripping means of the second ascender can be raised along the rope to a position where its associated handle when bearing a downward force is above the handle of the first ascender.
38. Apparatus as claimed in claim 37, wherein the handle of the first ascender is separated from the rope-gripping means thereof by a rigid or semi-rigid connection of length approximately equal to the reach of an average adult human's arm.
39. Apparatus as claimed in claim 38, wherein there is a direct connection between the rope-gripping means of the second ascender and its handle.
40. Apparatus as claimed in claim 37, wherein said separation between the rope-gripping means and its handle of the first ascender is provided by a rigid rod.
41. Apparatus as claimed in claim 37, wherein said separation between the rope-gripping means and its handle of the first ascender is provided by a flexible, load bearing component together with a less flexible component to provide thrust.
42. Apparatus as claimed in claim 41, wherein the flexible component is a cord, strap or the like and the component providing thrust is a rod.
43. Apparatus as claimed in claim 42, wherein the rod is made up of telescopic sections.
44. Apparatus as claimed in claim 42, wherein the rod is made up of foldable sections.
45. Apparatus as claimed in claim 42, wherein the rod is joined to the rope-gripping means of the first ascender or to its associated handle in such a way that limited relative longitudinal movement is permitted so that the cord, strap or the like can stretch when under load without the load becoming imposed on the rod.
46. Apparatus as claimed in claim 45, wherein the handle of the first ascender has a sleeve through which the rod passes, said rod having a stop to limit the relative movement of the sleeve and rod such that the rod can be lifted by the sleeve.
47. Apparatus as claimed in claim 45, wherein the rope gripping means of the first ascender has a sleeve through which the rod passes, said rod having a stop to limit the relative movement of the sleeve and rod such that the rod can lift the sleeve.
48. Apparatus as claimed in claim 37, wherein the rope-gripping means of the first ascender is of a type which can be released from and re-engaged with the rope using a spring-loaded lever and wherein a cord, cable or the like is provided whereby the climber can operate the lever.
49. Apparatus as claimed in claim 37, wherein the two ascender assemblies are linked by a strap, cord or the like which passes freely through an aperture in a component or components intended for attachment to a climbing harness, means being provided whereby the ends of the said strap cannot pass through the said aperture.
50. Apparatus as claimed in claim 49 wherein the component or components through which the strap, cord or the like linking the two ascender assemblies passes are two fall arresters or a bi-directional fall-arrester, the fall-arrester or arresters acting on the strap to prevent movement of the strap through the fall-arrester or arresters in either direction at more than a permitted speed.
51. Apparatus as claimed in claim 50, wherein two fall-arrest devices are joined side-by-side and to a pulley assembly, the strap passing through one of the fall-arrest devices, around the pulley and then through the other fall-arrest device.
52. Apparatus as claimed in claim 49, wherein knots at the ends of the said strap attaching it to the respective ascender assemblies are cravat knots allowing easy adjustment of the length of strap between the two handles as well as providing secure fixed attachments when load is applied to the strap.
 This invention relates to an improved apparatus for climbing a
rope, in particular a single rope suspended from above.
 Systems for climbing a single rope most commonly utilise a pair of rope-gripping devices known as "ascenders". An ascender is a device which, threaded onto or otherwise engaged with a rope, can be moved along the rope in one direction with little resistance. When a force is applied to the ascender in the opposite direction a mechanism grips and jams against to the rope, preventing it from moving along the rope in the direction of the applied force. This mechanism is usually a jamming cleat with ribs or teeth on its surface presented to the rope.
 Other rope-gripping devices are known as auto-locking or auto-braking belay devices. These latter devices are primarily used to abseil down a rope but some can also be utilised to ascend it.
 In normal use a pair of ascenders is engaged with a suspended rope and both are orientated so that they grip and jam the rope when a downward force is applied to them. The jamming of the rope of a first ascender of a pair enables it to support the climber's weight while the second ascender is moved upward along the rope to an elevated position. The climber's weight is then transferred to the second ascender, causing it to grip and jam the rope without moving downward along the rope and allowing the first ascender to in turn be moved upward along the rope to an elevated position.
 In some known systems the upper ascender of a pair has a handle which is grasped by one or both of the climber's hands while the lower ascender is attached to one or both of the climber's feet. The alternating movements of the ascenders permitted by this arrangement result in a "sit stand" climbing action.
 In another known system the ascenders have respective handles held by respective hands of the climber, respective foot-stirrups depending from each of the handles. This latter system permits a walking action of the climber's feet which leads to faster climbing. However a similar walking action of the climber's hands is not possible with the present forms of handled ascenders because the rope-gripping means of the two ascenders cannot pass one another along the rope. Consequently a chest harness is also required to assist in holding the climber upright, particularly when the climber's weight is transferred to the foot suspended from the lower ascender and the upper ascender is being moved upwards along the rope.
 A principal object of the present invention is to improve upon apparatus of the latter kind, permitting faster and less strenuous climbing, improved posture, greater freedom of movement and faster engagement with and disengagement from both the climber and the rope.
 In accordance with the present invention there is provided a pair of separate, handled rope-gripping devices for use in climbing a single rope suspended from above, characterised in that a first one of the devices which is to be engaged to the rope above the other, second device is separated from its handle by a rigid or semi-rigid connection of sufficient length that, in use of the devices and without detaching either device from the rope, the second device can be raised along the rope to a position where its handle is above the handle of the first device.
 Preferably there is a direct connection between the second device and its handle.
 Each of said devices is preferably an ascender, the ascenders being similar except for the extended connection between the first ascender and its handle.
 Preferably a foot stirrup is suspended from each handle.
 Preferably the length of said connection is not less than the reach of an average adult human's arm.
 The said connection may be provided by a rigid or semi-rigid rod attached at one end to the first-mentioned device and at its other end to the handle thereof.
 Alternatively said connection may comprise a flexible, load bearing component together with a less flexible component to provide thrust. The flexible component may be a cord, strap or the like and the component providing thrust may be a rod. The rod may be made up of telescopic sections or alternatively of foldable sections.
 Preferably the rod is joined to the first-mentioned device or to its associated handle in such a way that limited relative longitudinal movement is permitted so that the cord, strap or the like can stretch when under load without the load becoming imposed on the rod. The first-mentioned device or its associated handle may have a sleeve through which the rod passes, the rod having a stop such that it can be lifted by the sleeve.
 An advantage of the embodiment of the previous two paragraphs is that a cord, strap, length of webbing or the like can be employed capable of bearing an extreme weight, whereas the rod need have relatively little strength and can therefore be of a light-weight construction, convenient for transporting and handling.
 Where the first-mentioned device is of a type which can be released from and re-engaged with the rope by pulling a spring-loaded lever a cord, cable or the like may be provided alongside the said connection whereby the climber can operate the lever from the vicinity of the associated handle.
 The two devices may be linked by a strap, cord or the like which passes freely through an aperture in a component intended for attachment (directly or via another component) to the belay loop of a climbing harness, means being provided whereby the ends of the said strap cannot pass through the said eyehole aperture. The aperture preferably incorporates a pulley with the strap engaged around part of the circumference of the pulley wheel to reduce friction.
 Alternatively the two devices may be linked by a strap, cord of the like which passes through two fall-arresters, or a bi-directional fall-arrester, connected to the belay loop of a climbing harness, the fall-arrester or arresters acting oppositely on the strap to prevent movement of the strap through the fall-arrester or arresters in either direction at more than a permitted speed. This will ensure that if the climber has detached one of the devices from the rope and allows him/herself to fall outwardly from the rope as a result of releasing the handle of the other device the extent of that fall will be minimised by the bi-directional fall arrester or one or other of the two fall-arresters.
 The two fall-arrest devices may be joined side-by-side and to a pulley assembly, the strap passing through one of the fall-arrest devices, around the pulley and then through the other fall-arrest device.
 Knots at the ends of the said strap attaching them to the respective handles or to karabiners clipped to the handles are preferably Reinforced Prince Borna cravat knots allowing easy adjustment of the length of strap between the two handles as well as secure fixed attachments when load is applied to the strap.
 Alternatively the ends of the strap pass through adjustment buckles or are stitched, spliced or otherwise formed into loops in which the respective handles or karabiners clipped to the handles are held.
 In accordance with another aspect of the present invention there is provided handled, rope-gripping device for inclusion in the pair thereof defined in the fourteen preceding paragraphs, characterised in that the device is separated from its handle by a rigid or semi-rigid connection of length approximately equal to the reach of an average adult human's arm.
 Preferred embodiments of the invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which:
 FIG. 1 illustrates a first embodiment of the invention;
 FIGS. 2a to 2c are simplified illustrations of how the apparatus of FIG. 1 is used:
 FIG. 3 illustrates a second embodiment of the invention;
 FIGS. 4a and 4b illustrate a third embodiment of the invention, and
 FIG. 5 illustrates a fourth embodiment of the invention.
 Referring first to FIGS. 1 and 2, the apparatus illustrated comprises two ascenders 10a and 10b, each containing a rope jamming mechanism of the kind well known per se and each having an associated handle 11a and 11b. Foot stirrups 13a and 13b are suspended from the handles 11a and 11b by webbing straps 12a and 12b ends of which pass through length adjustment buckles 15a and 15b which are attached to locking karabiners 14a and 14b via loops of webbing 19a/20a and 19b/20b. The locking karabiners 14a and 14b are respectively attached to the ascender handles 11a and 11b. The lengths of the webbing straps 12a and 12b can be independently adjusted as required using adjusting buckles 15a and 15b so as to give the most effective simultaneous walking action of both hands and feet. Loops of elastic cord 16a and 16b are attached to the stirrups and can be stretched over the climber's feet to prevent them coming out of the stirrups during use.
 In order to prevent the climber from falling, two safety lines 18a and 18b consisting of nylon webbing connect the two ascender handles 11a and 11b to the belay loop 25 of a waist harness worn by the climber. Thus the climber is attached to both ascending devices at all times during use, providing increased safety. Connection of the safety lines to the handles and belay loop is via respective locking karabiners 14a, 14b and 17.
 The lengths of the two safety lines 18a and 18b can be independently adjusted near the belay loop 25 by passing them through adjusting buckles 22a and 22b, which are held captive in sewn nylon webbing loops 23a and 23b made from a single length of nylon webbing. The latter has a third sewn loop 24 at its mid point, through which the karabiner 17 is attached, providing the personal protective attachment point of the climber to the system. For optimum freedom of movement, the lengths of the safety lines 18a and 18b should be adjusted such that they allow the climber to raise the handles 11a and 11b as high above his head as his reach will allow while the karabiner 17 is attached to his waist harness.
 To eliminate the risk of the ends of the said safety lines passing through the adjustment buckles, both safety lines are comprised of one continuous length of webbing. Thus any excess length of webbing resulting from a shortening of the safety lines will form a bight of webbing 21, which can hang freely down behind the karabiner 17 and will therefore not interfere with the movement of the climber.
 As so far described the apparatus illustrated in FIG. 1 is conventional. In accordance with a first embodiment of the present invention, however, the ascender 10b is separated from the associated handle 11b by a rigid rod 26 the length of which is not less than the reach of an average adult human's arm, i.e. approximately 50 cm. The rod 26 is integral with the ascender 10b at one end and integral with the handle 11b at its other end and serves both as a strut for pushing ascender 10b upwards along the rope and as a tie for bearing the climber's weight when it is imposed on the handle 11b.
 The use of the apparatus of FIG. 1 is illustrated by FIGS. 2a to 2c. The apparatus is being used to climb a rope 28 which has been suspended from above, for example by being allowed to dangle from the branch of a tree. In order to show the climbing action more clearly the safety lines and their associated attachments and adjustment buckles and the foot stirrup adjustment buckles have been omitted. The climber has engaged the two ascenders 10a and 10b to the rope 28 with the ascender 10b above ascender 10a.
 In FIG. 2a the climber is momentarily at rest, standing up and placing his weight on one fully extended leg with the foot of that leg supported by the foot stirrup 13a. His weight therefore exerts a downward force on the ascender 10a causing it to jam the rope 28. The climber is using his corresponding hand to hold himself upright by holding the handle 11a. At this moment the climber exerts negligible or no downward force on the foot stirrup 13b and has therefore been able to raise the ascender 10b along the rope 28 by using his other hand to raise the handle 11b to the maximum height his reach will comfortably allow.
 Consequently the climber's other foot, which is in the foot stirrup 13b, has also been raised by the same distance.
 The climber now transfers his weight onto the foot supported by stirrup 13b and onto the handle 11b by using his arm to pull downwards on it so that his weight exerts a downward force on the ascender 10b causing it to jam the rope. At this moment the climber exerts negligible or no downward force on the foot stirrup 13a and is therefore able to commence raising the ascender 10a along the rope 28 by using his corresponding hand to raise the handle 11a while simultaneously standing up on the foot stirrup 13b and pulling down on the handle 11b.
 FIG. 2b illustrates an intermediate position. The climber is in the process of carrying out the upward movement which was at the point of commencement in FIG. 2a. FIG. 2b shows the moment in this movement at which the handle 11a has reached the same vertical position as the handle 11b and therefore has already been raised above the maximum vertical position that would have been possible had the ascender 10b and handle 11b been conventionally related. However because the ascender 10b is separated from the associated handle 11b by the connecting element 26 the climber is able to continue raising the handle 11a to the position illustrated in FIG. 2c while the ascender 10a remains below the ascender 10b.
 The climber's weight-bearing leg is now fully extended with its foot still being supported by the foot stirrup 13b. The climber's corresponding hand is also pulling on handle 11b to hold himself upright. The climber's other hand has now raised the handle 11a to the maximum height his reach will comfortably allow. Consequently the climber's other foot, which is in the foot stirrup 13a, has also been raised by the same distance. Being momentarily at rest once again the climber is now able to transfer his weight onto the foot stirrup 13a and the handle 11a causing the ascender 10a to jam the rope 28 and releasing the grip of the ascender 10b on the rope so that it can be moved upward.
 FIG. 3 illustrates an alternative embodiment of the invention. The upper ascender and its handle have been given the same reference numerals as their equivalents in FIGS. 1 and 2, but with a suffix '. Thus the ascender in FIG. 3 is denoted by 10b' and its associated handle by 11b'. The other components of the apparatus of this embodiment are similar to those of FIGS. 1 and 2 and are not shown in FIG. 3.
 In the arrangement of FIG. 3 the connection between the ascender 10b' and its handle 11b' comprises a length of webbing 29 which serves as a load-bearing tie. A second component of the connection between the ascender 10b' and its handle 11b' is a telescopic pole assembly 30, the three sections 30a, 30b and 30c of which contain locking mechanisms which can lock the sections in their extended condition. Such locking mechanisms are conventional in telescopic walking poles and do not need further explanation. The telescopic pole assembly serves as a strut capable of pushing the ascender 10b' upwards along the rope when the handle 11b' is raised.
 The benefit of this alternative embodiment is twofold: Firstly, by separating that part of the connecting element which must be strong enough in tension safely to bear the climber's weight--in the order of a metric tonne--from that part of the connecting element which need only be strong and rigid enough in compression to raise the ascender 10b' along the rope--in the order of a few kilograms--the heavy solid connecting element 26 illustrated in FIG. 1 can be replaced by the somewhat lighter length of webbing 29 and telescopic pole assembly 30. The other advantage of this embodiment is that the telescopic pole assembly 30 can be unlocked and retracted to less than half of its extended length making the apparatus easier to store and carry.
 The webbing 29 is attached to the ascender 10b' by passing one of its ends through a slot 31 in the body of the ascender and attaching it to the webbing that is on the other side of the slot with stitching 32, thus securing the ascender in a closed loop of webbing.
 The end of the telescopic pole with the smallest diameter 30a is fixed into a channel 35 on the body of the ascender 10b' orientated so that when the ascender is attached to a rope the telescopic pole is aligned parallel with the rope.
 The webbing 29 is attached to the handle 11b' by passing one of its ends through a slot 34 at the top of the body of the handle and attaching it to the webbing that is on the other side of the slot with stitching 33, thus securing the handle in a closed loop of webbing.
 The end of the telescopic pole with the largest diameter 30c passes through axially spaced apart sleeves 36 and 37 which have been formed by bending the side of the body of the handle 11b'. The internal diameter of the sleeves is slightly larger than the external diameter of the pole section 30c so as to allow for relative movement of the pole and handle during use.
 Sliding of the pole section 30c in the sleeves 36 and 37 allows the webbing 29 to stretch when bearing the climber's weight without that weight becoming imposed on the pole 30. However a stop 38 is provided on the pole section 30c between the sleeves 36 and 37. When the handle 11b' is lifted the stop 38 engages the sleeve 36 enabling the pole 30 to raise the ascender 10b'.
 Conventional rope-walking systems are not well suited to situations in which a suspended rope is deflected from a perfectly straight line by an obstruction and in these situations it is known that a `sit-stand` type arrangement, as described earlier, is preferable. A climber can easily switch to such a system during climbing by engaging with the rope a third ascender attached to his harness and then disengaging ascender 10b from the rope.
 However, as the apparatus illustrated in FIGS. 1 to 3 includes two handled ascenders in the region of the climbers head, the ascenders can be disengaged and reengaged with the rope one at a time to literally step over an obstruction. If the upper ascender is in accordance with the present invention then the length of obstruction which can be passed is increased due to the increased reach of the ascender. Consequently however, the spring-loaded lever which must be operated to re-engage the ascender with the rope above the obstruction may be beyond the climber's reach. As a solution to this problem a cord, cable or the like (not shown) may be provided attached to the lever and passing alongside the connection such as 26 to the region of the handle 11b. Preferably the cord passes through a conduit or is wound helically around the rod 26 to keep it within reach and to prevent fouling.
 In a further modification to the embodiment illustrated in FIG. 3 the telescopic pole 30 is replaced by a flexible rod (not shown) which, although sufficiently rigid to raise the associated ascender along the rope, would be capable of bending if it had to pass around an obstruction and the climber had then transferred his weight onto the associated handle. As a further solution to the same problem the said rod could be detachable from the handle so that the rod could remain straight when the climber is suspended from the handle.
 FIGS. 4a and 4b illustrate a further embodiment of the invention in which the connection between the handles 11a and 11b of the two ascenders is replaced by a single strap, cord or the like 41. Each end of the strap 41 is tied either directly to one of the ascender handles 11a,11b or to a respective karabiner (not shown) attached to an ascender handle. The main length of the said strap or cord 41 is able to pass freely through a captive eyehole 40 incorporated into a karabiner 39 which is attached to the belay loop of the climber's harness (not shown).
 In FIGS. 4a and 4b the link 41 between the ascender handles 11a and 11b is a length of webbing strap, which passes through a captive eyehole or ring 40 incorporated into a karabiner 39, the karabiner 39 being intended to be attached to the belay loop of the climber's harness.
 Preferably, to reduce friction, the eyehole 40 incorporates a pulley wheel (not shown) around part of the circumference of which the strap 41 runs.
 Each end of the strap 41 is tied around a respective ascender handle 11a or 11b with the well known `Reinforced Prince Borna` cravat knot 42a and 42b. For simplicity only the ascender handles and not their respective ascenders are shown.
 The free ends of the strap 41 are stitched into loops 43a and 43b, each of which holds captive a metal ring 44a and 441) to which the foot stirrups 12a and 12b are attached.
 FIG. 4a illustrates the position of the apparatus when both ascender handles 11a and 11b are at the same height (c.f. FIG. 2b) and FIG. 4b illustrates the system when one ascender handle is raised above the other (c.f. FIG. 2a or 2c).
 Thus when the climber is ascending by using a walking action of his hands holding the respective ascender handles 11a and 11b, the handle 11a which is being raised pulls more of the strap 41 through the eyehole 40, thus lengthening the section of strap 41a between the karabiner 39 and the handle 11a, and shortening the section of strap 41b between the karabiner 39 and the other handle 11b which is not being raised. The changing lengths of strap sections 41a and 41b ensure that there is minimal slack in the strap 41 at any point in the climbing action and therefore if the climber lets go of both of the ascender handles 11a, 11b then he would not fall any significant distance before the strap becomes tight and his weight is supported by both ascenders. The distance of fall in this case would be no more than a few centimetres due to the slack in the strap 41 plus any slack in the climber's harness.
 If, by way of deliberate misuse of the apparatus, the climber puts all of his weight on one of the ascenders and then detaches the other ascender from the rope and lets go of the handle of the first-mentioned ascender, he would fall until a stopper (in this case the actual attachment knot 42a or 42b) at the end of the strap at the detached handle reaches the captive eyehole 40. The said stopper, being too large to pass through the eyehole, would prevent any more of the strap 41 from passing through the eyehole 40 and the climber would thus be prevented from falling further and his weight would be supported by the first-mentioned ascender which is still attached to the rope. The maximum fall which could result from this misuse of the apparatus would be approximately 1 metre or less.
 A further measure to reduce the potential of falling by any significant distance should the climber let go of both of the ascender handles 11a and 11b or misuse the apparatus as described above would be to attach a third ascending device to the climber's harness and engage this with the climbing rope during the climb, although this would add more friction to the apparatus. If the third ascending device were an auto-locking/auto-braking belay device then this would allow the climber to switch from ascending to descending the rope with greater ease.
 In order to allow for the varying lengths of climbers' bodies and limbs, the apparatus can be adjusted as follows:
 The knot at each end of the strap 41 attaching it to the ascender handles (in this case a well known cravat knot, the `Reinforced Prince Borna` 42a and 42b), functions like a strap passing through an adjustment buckle and doubled-back (as one might find on a climbing harness) in that it can easily be loosened to allow the strap to be fed through the knot in order to adjust the length of the strap between the ascender handles 11a and 11b but will tighten and lock as soon as a force (such as the weight of the climber) is applied to the said strap 41.
 Once the length of strap 41 between the ascender handles 11a and 11b is adjusted to suit the climber as described above the lengths of the respective foot stirrup straps 12a and 12b can be adjusted by moving adjustment buckles 45a and 45b sewn into the ends of the foot stirrup straps along the same. The foot stirrup straps are doubled back through metal rings 44a and 44b and passed back through the said adjustment buckles. Similar methods of length adjustment are common in foot stirrups currently available.
 A modification of the embodiment of the invention of FIGS. 4a and 4b is illustrated in FIG. 5. Two fall-arresters 46a and 46b are connected together side-by-side and to a pulley 47. The strap 41 passes through one of the fall-arresters 46a and 46b, around the pulley 47 and then through the other fall-arrester. As in FIGS. 4a and 4b the ends 41a and 41b of the strap are connected to the handles 11a, 11b of the ascenders. The pulley assembly 47 is connected to the climber's harness 25 by a karabiner 39.
 Fall-arrest devices are well known in the art. One type allows free movement of a rope or strap through it at low speeds but responds to a shock load by engaging a clutch to grip the rope or strap when a critical speed is reached The two fall-arrest devices 46a and 46b act oppositely on the strap 41 so that in whichever direction a shock load is applied to the strap 41 one of the fall-arrest devices will arrest it. However if the strap 41 moves relatively slowly around the pulley 47 neither of the fall-arrest devices 46a and 46b will arrest it. With the arrangement of FIGS. 4a and 4b if one of the ascenders 10a or 10b is detached from the rope 28 and the climber lets go of the handle of the other ascender he/she will fall outwardly from the rope, rotating on the foot stirrup of the ascender which is still gripping to the rope. This will cause the ring 40, in the embodiment of FIGS. 4a and 4b, to travel rapidly to one extremity or the other of the strap 41 before the climber's fall is arrested. Using the arrangement of FIG. 5 if the strap 41 attempts to move rapidly around the pulley 47 in either direction it will be arrested by one or other of the fall-arresters 45a,46b so that the extent of the climber's fall is minimised.
 It will be appreciated that the two, distinct fall-arresters 46a and 46b could be replaced by a single, bi-directional fall arrester.
 For the avoidance of doubt the words "comprises" or "comprising" used in the appended claims are intended to mean both "consists of" and "includes".