The present invention relates to a fall arrest support and a tensioning device and a method for tensioning a fall arrest support particularly though not exclusively for use by linesmen working on electricity supply towers or pylons.

Conventionally, linesmen clip themselves onto a tower via bolts used for climbing the tower. This is renders the climb slow and awkward, with clipping continuously being overhead and un-clipping low down.

Fall arrest systems comprising a cable which extends continuously up the tower have been developed, a linesman clipping on at anti-climbing device level via a sliding cleat, which jams if he falls.

The cable of such a system should remain in tension. A slack cable can frap and fail due to wear and fatigue. Further, there is a problem that screw tensioning devices can relax causing re-tensioning to be necessary.

The object of the present invention is to provide improvements in a fall arrest system having a fall arrest support and tensioning of a cable of a fall arrest support.

According to a first aspect of the invention there is provided a support for arresting fall of a user from a structure, the support comprising:

• a cable and a one anchorage bracket, • the one anchorage bracket having:

• means for securement to a first part of a structure and

• means for fastening of one end of the cable to the one anchorage bracket,

• the cable being of wire and having:

• a first attachment load-bearingly attached to the one end of the cable, this attachment being complementary to the fastening means of the one anchorage bracket for transferring fall load from the cable to the anchorage bracket,

• a second attachment load-bearingly attached to the other end of the cable and adapted at one part thereof for applying standing tension to the cable by means of a tensioning device and adapted at another part thereof for anchorage of this second attachment to a second part of the structure, or another anchorage bracket attached thereto, for reacting of the standing tension in the cable for its maintenance by the structure and

• a lockable fitting for acting directly between the second part of the structure, or other anchorage bracket, to react the standing tension in the cable on removal of the tensioning device from the said one part thereof.

hi one embodiment, the second attachment comprises a threaded bar, having a bore into which the other end of the cable is load-bearingly attached by swaging and the lockable fitting is a nut on the threaded bar, the thread being of sufficient length to permit fitting of the nut, a lock nut and a tensioning device to the distal end of the thread, with the bar passing through the second part of the structure, or other anchorage bracket.

In this embodiment, the one anchorage bracket comprises:

• two L pieces adapted to fit an angle iron of a structure and having apertures towards their distal ends and

• a pair of clamping nuts and bolts at the apertures, one of the pair holding the fastening means in use.

In another embodiment: • the second attachment comprises:

• a collar load-bearingly swaged onto at the other end of the cable,

• a load transfer bracket and

• a said other anchorage bracket,

• the load transfer bracket having: • a sleeve through which the cable passes and against which the swaged-on collar abuts in use,

• the sleeve and the swaged-on collar being dimensioned for passage over them of a fall arrest cleat and

• the sleeve being attached to a body of the load transfer bracket by a tongue and • the lockable fitting is a screw thread clamp acting at a longitudinal adjustment in one of the pair of the load transfer and the other anchorage brackets for clamping the brackets together after tensioning of the cable, the longitudinal adjustment being parallel to the sleeve.

Whilst the longitudinal adjustment can be envisaged to be a series of drillings, preferably, it is a slot. In the preferred embodiment, the slot is in the load transfer bracket and the slot is of sufficient length to allow both coupling of the tensioning device at the sleeve and extension of the cable on tensioning.

Conveniently, the sleeve is lined with plastics material for protecting the cable from rubbing on the sleeve, both the cable and the sleeve being of stainless steel.

Again other configurations can be envisaged for the longitudinal adjustment and the lockable fitting such as a U bolt engaging in apertures in one of and the other anchorage bracket and an elongate part on the other, the U bolt when tightened clamping the elongate part against the bracket. In the preferred embodiment, the clamping means comprises a slotted part on the load transfer bracket and a captive head bolt received in a bore on the other anchorage bracket. This arrangement is easy to clamp, particularly with a torque wrench, and secure, particularly by use of an anti- vibration washer under a clamping nut.

Preferably:

• each of the anchorage brackets is adapted to be connected to the structure by a respective bolt for climbing the structure and includes a respective boss for reacting against the structure and holding the orientation of its bracket about its bolt on tensioning of the cable; • the load transfer bracket and the other anchorage bracket are each provided a respective one of a pair of opposed tension-force abutment points for reacting standing-tension force applied by the tensioning device prior to locking of the lockable fitting;

• the other anchorage bracket comprises an angled plate, one part of which in use abuts a flange of a structure's corner angle iron and the other, off-angled part extends at an angle to bring the cable close to the bisector of the structure's corner angle; • the other anchorage bracket further comprises several bores in the first part for selection of a suitable one to receive a climbing bolt for the body's fixture to the structure;

• the said one anchorage bracket has an arm angled off from a plate adapted to be connected by a climbing bolt, the arrangement being such that tension in the cable exerts a bending moment in the plate, the bracket being dimensioned for energy absorbing plastic deflection in event of an arrested fall.

According to a second aspect of the invention there is provided a tensioning device for a cable of a support of the first aspect for arresting fall of a user from a structure, the tension force applicator comprising:

• a body,

• a tension connector and a tensile member movably mounted on the body, the tension connector being complementary to the tension application adaption of the said second attachment of the cable, • a compression abutment rigid with the body, the abutment being complementary to a said second part of the structure, or a said other anchorage bracket attached thereto,

• jack means for drawing the tensile member with respect to the body and

• a compression spring arranged between the jack means and the body, for applying an equal and opposite tensile force to the tension connector to that applied by the jack means to the compression spring.

Preferably:

• the jack comprises a nut on a threaded bar, which can be the tensile member; • the compression spring is a coil spring having a spring rate and length such that it becomes coil bound at the required standing tension;

• a tensioning device includes a stop for relieving the coil spring of excessive compression in event of the tension applied exceeding the coil bound compression of the spring.

Where the second attachment is a threaded bar, the tension connector is threaded complementarily with the threaded bar.

Where the second attachment has a load transfer bracket, the tension connector is complementary with the load transfer bracket and the compression abutment is complementary with the other anchorage bracket.

In the preferred embodiment of the force applicator, the one of the force application points reacts — as mentioned above - at the end of the slot in the load transfer bracket. It is a pin and is sprung loaded to an operative position engaging the slot. The force applicator has a hub provided with a mortise into which the slotted end of the cable holder fits. The pin is withdrawn against a spring for fitting the slotted end into the mortise and once the pin is released into the slot, the hub is captive on the cable holder.

Again in the preferred embodiment, the hub has two clearance bores and a central threaded bore, all three being parallel to the mortise. The clearance bores accommodate thrust rods which are joined at one end by a pusher, having a nib for abutting the body of the bracket, thus constituting the other force application point. Their other ends are connected to a spring reaction plate. The threaded bar is engaged in the threaded bore and carries a compression spring, a spring compression plate and a nut, tightening of the nut compresses the spring with a force which is transferred to the cable.

The spring is designed to indicate that the design tension is being applied to the cable by bottoming - i.e. becoming coil-bound - when applying the design tension.

According to a third aspect of the invention there is provided a support of the first aspect and a tensioning device of the second aspect.

According to a fourth aspect of the invention there is provided a method of tensioning cable of a support for arresting fall of a user from a structure with a tensioning device, the method consisting in the steps of: • securing the one anchorage bracket to the first part of the structure;

• fastening the one end of the cable to the one anchorage bracket;

• connecting the other part of the second attachment to a second part of the structure or another anchorage bracket secured to the second part of the structure; • applying a tensioning device to the one part of the second attachment;

• tensioning the cable to its standing tension;

• locking the second attachment to the second part of the structure or the other anchorage bracket; and

• removing the tensioning device.

Normally the force applicator will be removed for use with another fall arrest support. However, it can be envisaged the tensing device could be provided integral with its bracket. In this case, it would be relaxed after clamping of the load transfer bracket, to provide that the cable is held in tension by action of the clamp as opposed to the action of the force applicator in case the latter relaxes over time as is known to be a problem with existing tensioning devices.

Whilst it is possible that the system can be installed with a fixed length of cable, usually the top and bracket will fixed at location in the tower whose separation varies in accordance with the usual stack up of tolerances.

The tensioning method can include the preliminary operation of adjusting the length of the cable, the adjustment consisting in the steps of:

• swaging the one end of the cable to the first attachment or a component thereof;

• locating a collar to be swaged at an abutment provided on the second attachment, the collar being a component of the second attachment, the other part of the second attachment having been connected;

• temporarily tightening the cable and noting the position of the collar; and

• swaging the collar to the cable in this position.

To help understanding of the invention, two specific embodiments thereof will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a fall arrest support in accordance with the invention installed at the corner post of a pylon;

Figure 2 is front view of a cable tensioner in accordance with the invention; Figure 3 is a side view of the cable tensioner of Figure 2;

Figure 4 is a side view of the cable tensioner in use tensioning the cable of the fall arrest system of Figure 1;

Figure 5 is a side view of similar to Figure 4 of a tail in use with the fall arrest system of Figure 1; Figure 6 is a side view of a second fall arrest support installed along an arm of a pylon;

Figure 7 is a more detailed side view (from the opposite side from Figure 6) of attachment of the support to a corner angle iron of at the arm;

Figure 8 is a similar detailed side view of attachment of the support towards the outer end of the arm; and

Figure 9 is a detailed view of the support being tensioned.

Referring to Figure 1, the fall arrest system shown in the drawings comprises a top. anchorage bracket 1, a bottom anchorage bracket 2, (in practice a number of intermediate brackets - not shown) and a cable 3 between the brackets. The brackets are fixed to a pylon P - of which part only is shown in the form of corner angle irons C with flanges F. Climbing bolts B are used for fixing the brackets to the flanges F via one of a plurality of bores 11 ,21 in fixture ends 12,22 of the brackets. The fixture ends carry bosses 13,23 in their bottom and top edges 14,24 respectively. Cable tension pulls the distal ends of the brackets towards each other about the bolts B and the bosses react with the corner angle irons at the corner between the flanges F and their other flanges Ff and limit the extent to which the brackets can pivot towards each other about the bolts.

The distal ends of the brackets - or at least an arm 15 in the case of the top anchorage bracket and an arm 25 in the case of the bottom anchorage bracket - are angled off to place the cable in the bisector plane of the flanges F ₅ Ff. The top of the cable is connected to the bracket end 15 by means of a swaged on clevis pin fitting 16. The end 15 is dimensioned such that in the event of a fall and loading of the cable, the bracket deforms plastically, peeling away from the face F.

The bottom anchorage bracket is more complex, in that the arm 25 has a bore for a clamp bolt 31 , carrying a load transfer bracket 32, an anti-vibration washer 33 and a clamp nut 34. The bolt is engaged in a slot 35 in a limb 36 of the bracket 32. Above the limb, it is integrally connected via a thin tongue 37 to a sleeve 38 having a polyamide liner 39 for the end of the cable. This extends through the sleeve to a swaged on collar 40, the collar having been swaged in situ to take account of the actual distance from top anchorage bracket. The bottom end of the limb has a link 41 between two fingers 42 defining the slot between them. The slot is rebated to hold the bolt 31 against rotation.

Turning to Figure 2 to 4, a cable tensioning device 51 is shown. It has a hub 52 designed to be connected to the load transfer bracket 32. Extending through the hub, via clearance bores 53 are a pair of push rods 54, connected at one end by a bridge 55 with a nib 56 and at the other end by a disc 57. A threaded rod 59 extends from a threaded bore 60 in the hub, where it is fast, and through the disc 57 via a central, clearance bore 61. The disc forms an abutment for a compression coil spring 62, itself captivated by a further disc 63 held by a nut 64 on the free end of the rod 59.

For use, a pin 83 is drawn out against the action of an internal spring 65 to allow the limb 36 to pass into a mortise 66 in the hub 52. With the hub pushed onto the arm and the pin released, the latter engages the link 41 securing the tensioning device against removal from the arm. The nib 56 projects through the slot 35 for abutment against the arm 25 of the bottom anchorage bracket 2 as the nut 64 is tightened. Initially, on tightening, the tension in the cable is small in comparison with force required to compress the spring. As the slack is taken up in the cable, further tightening of the nut tensions the cable and compresses the spring as the limb 36 is

urged downwards by the hub 52, with the nib pushing against bracket. Continued tightening ultimately causes the spring to become coil bound. A sleeve 67 inside the spring avoids over-compression of the spring. The force required to render the spring coil bound is that necessary to tension the cable for use and impose a small elastic deformation in the brackets. With this tension applied, the clamp nut 34 is tightened to a determined torque such that the tensioning device can be relaxed and removed, with the cable still correctly tensioned. When the cable is new, it will close its lay-up somewhat after a few days, leading to a slight relaxation in tension. However, this is accommodated by the elastic deformation of the brackets and indeed the elastic stretching of the cable. Thus the cable remains permanently tensioned, in particular since there are no springs as such nor screw devices imposing the tension, such as have shown themselves liable to relax in prior devices.

The bottom bracket will normally be installed above an anti-climbing device on a tower or pylon. For providing fall arrest between the bottom bracket and the ground a tail 71, having a hub 72 and sprung pin 73 analogous to the hub 52 and pin 63, can be connected temporarily to the limb 36. The tail has a sleeve 74 which comes into alignment with the sleeve 38, the sleeve supporting a tail cable 75 via a swage 76. Thus a user can connect onto the tail at ground level and climb through the anti-climbing device (now opened) as far up the tower as the fall arrest system extends.

Turning now to Figures 6 to 9, a second fall arrest cable 103 is shown extending along a side arm A of a pylon. At its outer end, the cable is secured by an outer anchorage bracket 101 to an angle-iron, diagonal member D of the arm A between and upper raker UR and a lower racker LR. The bracket comprises to L- members 1011, 1012, each having a slots 1013 towards their ends for bolts 1014 drawing the members tight against the diagonal D. One of the bolts fastens an eye 1015, which accommodates the head of a T piece 116 into a stem 1161 of which the end of the cable 103 is swaged.

At its inner end, the cable has a 16mm diameter threaded bar 102 swaged onto it, the cable being 8mm in diameter. The bar 102 is positioned in place of a climbing bolt at the latter' s drilling in the flange F of the corner angle iron C of the pylon. The

position of the outer anchorage bracket is adjusted to provide for the cable to run reasonably horizontally from the bar 102. This is secured in position with a pair of nuts 1021 gripping opposite sides of the flange F.

For tensioning the cable, a tensioning device 151 is provided. It has a body

1511 having an end abutment surface 1512 and a central bore 1513 in a lateral flange 1514. Accommodated in this is a shaft 1515, having a threaded adapter 1516 fast with it. The adapter has a bore 1517 threaded with an Ml 6 thread, complementarily with the thread of the bar 102. On the other side of the flange 1514, the rod carries a rated compression spring 1518, which has a spring rate and length such that it exerts a force equal to that required in the cable when it is coil bound. A washer 1519 and a nut 15110 are provided outside the spring. For tensioning the cable, the adapter 1516 is screwed onto the bar 102, with the nuts, in particular that on the cable side of the flange F, slackened off. The nut 15110 is tightened until the spring is coil bound and the cable is tensioned. Via a cutout 15111 in the body, the nut 1021 on the side of the flange F remote from the cable is tightened. The bar is then locked in place by means of the nut on the cable side of the flange. With the cable thus tensioned, the tensioning device is released and removed.

In use, a user clippers himself to the cable via a karabiner at the end of a fall arrest lanyard. The same cleat as used with the vertical cable 3 cannot be used, since the end of the cable is not accessible. It is possible, though more costly to introduce a cable end attachment such as the lower one on the vertical cable. However, this is more costly and the use of the bar replacing the climbing bolt enables a user to climb higher on the pylon than the arm having the cable 103.

The invention is not intended to be restricted to the details of the above described embodiments. For instance, the thread and spring tensioning device of Figures 2,3 and 4, can be replaced by an hydraulic device in which the actuation from the nut and threaded rod and the force regulation from the spring can be provided by a piston and cylinder device having a pressure gauge or relief valve for indicating application of the desired tension to the fall arrest cable.

It should be noted that whilst the invention was primarily intended for use on towers such as pylons, it is equally applicable to towers in the form of radio masts, or other structures requiring to be